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Bug 1804420

Summary:	Can we get an updated kpartx that supports more than 256 loop devices for RHEL7?
Product:	Red Hat Enterprise Linux 7	Reporter:	Yulia <ysudarev>
Component:	device-mapper-multipath	Assignee:	Ben Marzinski <bmarzins>
Status:	CLOSED ERRATA	QA Contact:	Lin Li <lilin>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	7.7	CC:	agk, bmarzins, heinzm, jbrassow, kzak, lilin, msnitzer, prajnoha
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Linux
Whiteboard:
Fixed In Version:	device-mapper-multipath-0.4.9-132.el7	Doc Type:	Bug Fix
Doc Text:	Cause: kpartx only looks for loop devices with minor numbers 0 - 255, when trying to find a loop device Consequence: kpartx does not correctly handle more than 256 loop devices Fix: kpartx now will look in sysfs to find the loop devices, and accept minor number larger than 255 Result: kpartx now works corrctly on setups with more than 256 loop devices	Story Points:	---
Clone Of:		Environment:
Last Closed:	2020-09-29 20:01:05 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Yulia 2020-02-18 19:20:13 UTC

Description of problem:

Need upgraded kpartx that supports more than 256 loop devices. 


Confirmed, it's pretty explicit in kpartx that we only check 256 loops:

<snip>
extern char *
find_loop_by_file (const char * filename)
{
        char dev[64];
        char *loop_formats[] = { "/dev/loop%d", "/dev/loop/%d" };
        int i, j, fd;
        struct stat statbuf;
        struct loop_info loopinfo;

        for (j = 0; j < SIZE(loop_formats); j++) {

                for (i = 0; i < 256; i++) {
                        sprintf (dev, loop_formats[j], i);

                        if (stat (dev, &statbuf) != 0 ||
                            !S_ISBLK(statbuf.st_mode))
                                continue;

                        fd = open (dev, O_RDONLY);
...
</snip>

The referenced patch that Mike notes was added upstream to correct that:

https://github.com/openSUSE/multipath-tools/commit/0d83956858a946817cd09b818d70de010f7bdd76

RHEL8 does have (a slightly modified) version of this so would handle > 256 natively. The challenge is going to be the limited scope of what we can include in RHEL7 at this stage in its lifecycle. We'll propose this with engineering and ideally if we're targeting work at dm-multipath that we can add this as a low-hanging fruit to that since I don't expect that it'll be sufficient itself to trigger an erratum (kpartx is part of the device-mapper-multipath packageset so isn't quite so isolated).

Comment 2 Karel Zak 2020-02-19 15:40:57 UTC

kpartx is not the same tool like partx from util-linux (where we support an unlimited number of loop devices since year 2011)

 # rpm -qif /usr/sbin/kpartx | grep Source
 Source RPM  : device-mapper-multipath-0.8.0-3.fc31.src.rpm

Reassigning...

And yes, find_loop_by_file() seems pretty stupid as we have (for years) a nice kernel interface to ask for free loop devices. 

Maybe we really need libloopblk to avoid the same thing in mount, losetup, cryptsetup, kpartx, etc... :-)

Comment 3 Ben Marzinski 2020-02-19 20:48:30 UTC

(In reply to Karel Zak from comment #2)
> kpartx is not the same tool like partx from util-linux (where we support an
> unlimited number of loop devices since year 2011)
> 
>  # rpm -qif /usr/sbin/kpartx | grep Source
>  Source RPM  : device-mapper-multipath-0.8.0-3.fc31.src.rpm
> 
> Reassigning...
> 
> And yes, find_loop_by_file() seems pretty stupid as we have (for years) a
> nice kernel interface to ask for free loop devices. 

Yeah, but this isn't asking for a free loop device. It is looking to see if the file in question is associated with an already in-use loop device. I agree that the 256 device limit is wrong, but unless I'm missing something, there is no way to ask /dev/loop-control if a specific file is associated with a loop device. You just got to go through them all and look. right?

And since this is a bug with an existing fix, that just needs to be backported, I don't think it will be a problem for putting in 7.9.

Comment 4 Karel Zak 2020-02-20 10:30:06 UTC

> Yeah, but this isn't asking for a free loop device.

Ah, I didn't read it carefully. Sorry.

> but unless I'm missing something,
> there is no way to ask /dev/loop-control if a specific file is associated
> with a loop device. You just got to go through them all and look. right?

Yes, you need to scan all loop devices in this case.

In util-linux we use /sys/block/<name>/loop/backing_file rather than ioctl on /dev/loop. The ioctl
uses small fixed buffer (64 bytes!) for all the path and you need root perms to get this info. 
The attribute file in /sys has no these restrictions.

For example:

 https://github.com/karelzak/util-linux/blob/master/lib/loopdev.c#L515

> And since this is a bug with an existing fix, that just needs to be
> backported, I don't think it will be a problem for putting in 7.9.

Yeap, good enough for RHEL-7 ;-)

Comment 10 Lin Li 2020-07-09 06:02:10 UTC

Reproduced on device-mapper-multipath-libs-0.4.9-127
[root@storageqe-06 ~]# rpm -qa | grep multipath
device-mapper-multipath-libs-0.4.9-127.el7.x86_64
device-mapper-multipath-0.4.9-127.el7.x86_64

[root@storageqe-06 ~]# rpm -qa | grep kpartx
kpartx-0.4.9-127.el7.x86_64

create 299 loop devices using below scripts. 
[root@storageqe-06 ~]# cat loop.sh 
for ((i=1;i<300;i++))
do
 dd if=/dev/zero of=FS_on_file$i bs=1k count=10000
   losetup /dev/loop$i FS_on_file$i
   mkfs -t ext3 /dev/loop$i
   mkdir /mnt/FS_file$i
   mount /dev/loop$i /mnt/FS_file$i
done 


[root@storageqe-06 ~]# lsblk
NAME                        MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                           8:0    0 136.7G  0 disk  
sdb                           8:16   0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                            253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                            253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                            253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                            253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                            253:8    0     2G  0 lvm   [SWAP]
sdc                           8:32   0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                            253:0    0     2G  0 mpath 
sdd                           8:48   0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                            253:3    0     2G  0 mpath 
sde                           8:64   0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                            253:1    0     2G  0 mpath 
sdf                           8:80   0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                            253:2    0     2G  0 mpath 
sdg                           8:96   0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                            253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                            253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                            253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                            253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                            253:8    0     2G  0 lvm   [SWAP]
sdh                           8:112  0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                            253:0    0     2G  0 mpath 
sdi                           8:128  0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                            253:3    0     2G  0 mpath 
sdj                           8:144  0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                            253:1    0     2G  0 mpath 
sdk                           8:160  0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                            253:2    0     2G  0 mpath 
sdl                           8:176  0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                            253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                            253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                            253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                            253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                            253:8    0     2G  0 lvm   [SWAP]
sdm                           8:192  0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                            253:0    0     2G  0 mpath 
sdn                           8:208  0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                            253:3    0     2G  0 mpath 
sdo                           8:224  0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                            253:1    0     2G  0 mpath 
sdp                           8:240  0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                            253:2    0     2G  0 mpath 
sdq                          65:0    0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                            253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                            253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                            253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                            253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                            253:8    0     2G  0 lvm   [SWAP]
sdr                          65:16   0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                            253:0    0     2G  0 mpath 
sds                          65:32   0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                            253:3    0     2G  0 mpath 
sdt                          65:48   0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                            253:1    0     2G  0 mpath 
sdu                          65:64   0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                            253:2    0     2G  0 mpath 
sr0                          11:0    1  1024M  0 rom   
loop0                         7:0    0   9.8M  0 loop  /mnt/FS_file1
loop1                         7:1    0   9.8M  0 loop  /mnt/FS_file1
loop2                         7:2    0   9.8M  0 loop  /mnt/FS_file2
loop3                         7:3    0   9.8M  0 loop  /mnt/FS_file3
loop4                         7:4    0   9.8M  0 loop  /mnt/FS_file4
loop5                         7:5    0   9.8M  0 loop  /mnt/FS_file5
loop6                         7:6    0   9.8M  0 loop  /mnt/FS_file6
loop7                         7:7    0   9.8M  0 loop  /mnt/FS_file7
loop8                         7:8    0   9.8M  0 loop  /mnt/FS_file8
loop9                         7:9    0   9.8M  0 loop  /mnt/FS_file9
loop100                       7:100  0   9.8M  0 loop  /mnt/FS_file100
loop101                       7:101  0   9.8M  0 loop  /mnt/FS_file101
loop102                       7:102  0   9.8M  0 loop  /mnt/FS_file102
loop103                       7:103  0   9.8M  0 loop  /mnt/FS_file103
loop104                       7:104  0   9.8M  0 loop  /mnt/FS_file104
loop105                       7:105  0   9.8M  0 loop  /mnt/FS_file105
loop106                       7:106  0   9.8M  0 loop  /mnt/FS_file106
loop107                       7:107  0   9.8M  0 loop  /mnt/FS_file107
loop108                       7:108  0   9.8M  0 loop  /mnt/FS_file108
loop109                       7:109  0   9.8M  0 loop  /mnt/FS_file109
loop110                       7:110  0   9.8M  0 loop  /mnt/FS_file110
loop111                       7:111  0   9.8M  0 loop  /mnt/FS_file111
loop112                       7:112  0   9.8M  0 loop  /mnt/FS_file112
loop113                       7:113  0   9.8M  0 loop  /mnt/FS_file113
loop114                       7:114  0   9.8M  0 loop  /mnt/FS_file114
loop115                       7:115  0   9.8M  0 loop  /mnt/FS_file115
loop116                       7:116  0   9.8M  0 loop  /mnt/FS_file116
loop117                       7:117  0   9.8M  0 loop  /mnt/FS_file117
loop118                       7:118  0   9.8M  0 loop  /mnt/FS_file118
loop119                       7:119  0   9.8M  0 loop  /mnt/FS_file119
loop120                       7:120  0   9.8M  0 loop  /mnt/FS_file120
loop121                       7:121  0   9.8M  0 loop  /mnt/FS_file121
loop122                       7:122  0   9.8M  0 loop  /mnt/FS_file122
loop123                       7:123  0   9.8M  0 loop  /mnt/FS_file123
loop124                       7:124  0   9.8M  0 loop  /mnt/FS_file124
loop125                       7:125  0   9.8M  0 loop  /mnt/FS_file125
loop126                       7:126  0   9.8M  0 loop  /mnt/FS_file126
loop127                       7:127  0   9.8M  0 loop  /mnt/FS_file127
loop128                       7:128  0   9.8M  0 loop  /mnt/FS_file128
loop129                       7:129  0   9.8M  0 loop  /mnt/FS_file129
loop130                       7:130  0   9.8M  0 loop  /mnt/FS_file130
loop131                       7:131  0   9.8M  0 loop  /mnt/FS_file131
loop132                       7:132  0   9.8M  0 loop  /mnt/FS_file132
loop133                       7:133  0   9.8M  0 loop  /mnt/FS_file133
loop134                       7:134  0   9.8M  0 loop  /mnt/FS_file134
loop135                       7:135  0   9.8M  0 loop  /mnt/FS_file135
loop136                       7:136  0   9.8M  0 loop  /mnt/FS_file136
loop137                       7:137  0   9.8M  0 loop  /mnt/FS_file137
loop138                       7:138  0   9.8M  0 loop  /mnt/FS_file138
loop139                       7:139  0   9.8M  0 loop  /mnt/FS_file139
loop140                       7:140  0   9.8M  0 loop  /mnt/FS_file140
loop141                       7:141  0   9.8M  0 loop  /mnt/FS_file141
loop142                       7:142  0   9.8M  0 loop  /mnt/FS_file142
loop143                       7:143  0   9.8M  0 loop  /mnt/FS_file143
loop144                       7:144  0   9.8M  0 loop  /mnt/FS_file144
loop145                       7:145  0   9.8M  0 loop  /mnt/FS_file145
loop146                       7:146  0   9.8M  0 loop  /mnt/FS_file146
loop147                       7:147  0   9.8M  0 loop  /mnt/FS_file147
loop148                       7:148  0   9.8M  0 loop  /mnt/FS_file148
loop149                       7:149  0   9.8M  0 loop  /mnt/FS_file149
loop150                       7:150  0   9.8M  0 loop  /mnt/FS_file150
loop151                       7:151  0   9.8M  0 loop  /mnt/FS_file151
loop152                       7:152  0   9.8M  0 loop  /mnt/FS_file152
loop153                       7:153  0   9.8M  0 loop  /mnt/FS_file153
loop154                       7:154  0   9.8M  0 loop  /mnt/FS_file154
loop155                       7:155  0   9.8M  0 loop  /mnt/FS_file155
loop156                       7:156  0   9.8M  0 loop  /mnt/FS_file156
loop157                       7:157  0   9.8M  0 loop  /mnt/FS_file157
loop158                       7:158  0   9.8M  0 loop  /mnt/FS_file158
loop159                       7:159  0   9.8M  0 loop  /mnt/FS_file159
loop160                       7:160  0   9.8M  0 loop  /mnt/FS_file160
loop161                       7:161  0   9.8M  0 loop  /mnt/FS_file161
loop162                       7:162  0   9.8M  0 loop  /mnt/FS_file162
loop163                       7:163  0   9.8M  0 loop  /mnt/FS_file163
loop164                       7:164  0   9.8M  0 loop  /mnt/FS_file164
loop165                       7:165  0   9.8M  0 loop  /mnt/FS_file165
loop166                       7:166  0   9.8M  0 loop  /mnt/FS_file166
loop167                       7:167  0   9.8M  0 loop  /mnt/FS_file167
loop168                       7:168  0   9.8M  0 loop  /mnt/FS_file168
loop169                       7:169  0   9.8M  0 loop  /mnt/FS_file169
loop170                       7:170  0   9.8M  0 loop  /mnt/FS_file170
loop171                       7:171  0   9.8M  0 loop  /mnt/FS_file171
loop172                       7:172  0   9.8M  0 loop  /mnt/FS_file172
loop173                       7:173  0   9.8M  0 loop  /mnt/FS_file173
loop174                       7:174  0   9.8M  0 loop  /mnt/FS_file174
loop175                       7:175  0   9.8M  0 loop  /mnt/FS_file175
loop176                       7:176  0   9.8M  0 loop  /mnt/FS_file176
loop177                       7:177  0   9.8M  0 loop  /mnt/FS_file177
loop178                       7:178  0   9.8M  0 loop  /mnt/FS_file178
loop179                       7:179  0   9.8M  0 loop  /mnt/FS_file179
loop180                       7:180  0   9.8M  0 loop  /mnt/FS_file180
loop181                       7:181  0   9.8M  0 loop  /mnt/FS_file181
loop182                       7:182  0   9.8M  0 loop  /mnt/FS_file182
loop183                       7:183  0   9.8M  0 loop  /mnt/FS_file183
loop184                       7:184  0   9.8M  0 loop  /mnt/FS_file184
loop185                       7:185  0   9.8M  0 loop  /mnt/FS_file185
loop186                       7:186  0   9.8M  0 loop  /mnt/FS_file186
loop187                       7:187  0   9.8M  0 loop  /mnt/FS_file187
loop188                       7:188  0   9.8M  0 loop  /mnt/FS_file188
loop189                       7:189  0   9.8M  0 loop  /mnt/FS_file189
loop190                       7:190  0   9.8M  0 loop  /mnt/FS_file190
loop191                       7:191  0   9.8M  0 loop  /mnt/FS_file191
loop192                       7:192  0   9.8M  0 loop  /mnt/FS_file192
loop193                       7:193  0   9.8M  0 loop  /mnt/FS_file193
loop194                       7:194  0   9.8M  0 loop  /mnt/FS_file194
loop195                       7:195  0   9.8M  0 loop  /mnt/FS_file195
loop196                       7:196  0   9.8M  0 loop  /mnt/FS_file196
loop197                       7:197  0   9.8M  0 loop  /mnt/FS_file197
loop198                       7:198  0   9.8M  0 loop  /mnt/FS_file198
loop199                       7:199  0   9.8M  0 loop  /mnt/FS_file199
loop200                       7:200  0   9.8M  0 loop  /mnt/FS_file200
loop201                       7:201  0   9.8M  0 loop  /mnt/FS_file201
loop202                       7:202  0   9.8M  0 loop  /mnt/FS_file202
loop203                       7:203  0   9.8M  0 loop  /mnt/FS_file203
loop204                       7:204  0   9.8M  0 loop  /mnt/FS_file204
loop205                       7:205  0   9.8M  0 loop  /mnt/FS_file205
loop206                       7:206  0   9.8M  0 loop  /mnt/FS_file206
loop207                       7:207  0   9.8M  0 loop  /mnt/FS_file207
loop208                       7:208  0   9.8M  0 loop  /mnt/FS_file208
loop209                       7:209  0   9.8M  0 loop  /mnt/FS_file209
loop210                       7:210  0   9.8M  0 loop  /mnt/FS_file210
loop211                       7:211  0   9.8M  0 loop  /mnt/FS_file211
loop212                       7:212  0   9.8M  0 loop  /mnt/FS_file212
loop213                       7:213  0   9.8M  0 loop  /mnt/FS_file213
loop214                       7:214  0   9.8M  0 loop  /mnt/FS_file214
loop215                       7:215  0   9.8M  0 loop  /mnt/FS_file215
loop216                       7:216  0   9.8M  0 loop  /mnt/FS_file216
loop217                       7:217  0   9.8M  0 loop  /mnt/FS_file217
loop218                       7:218  0   9.8M  0 loop  /mnt/FS_file218
loop219                       7:219  0   9.8M  0 loop  /mnt/FS_file219
loop220                       7:220  0   9.8M  0 loop  /mnt/FS_file220
loop221                       7:221  0   9.8M  0 loop  /mnt/FS_file221
loop222                       7:222  0   9.8M  0 loop  /mnt/FS_file222
loop223                       7:223  0   9.8M  0 loop  /mnt/FS_file223
loop224                       7:224  0   9.8M  0 loop  /mnt/FS_file224
loop225                       7:225  0   9.8M  0 loop  /mnt/FS_file225
loop226                       7:226  0   9.8M  0 loop  /mnt/FS_file226
loop227                       7:227  0   9.8M  0 loop  /mnt/FS_file227
loop228                       7:228  0   9.8M  0 loop  /mnt/FS_file228
loop229                       7:229  0   9.8M  0 loop  /mnt/FS_file229
loop230                       7:230  0   9.8M  0 loop  /mnt/FS_file230
loop231                       7:231  0   9.8M  0 loop  /mnt/FS_file231
loop232                       7:232  0   9.8M  0 loop  /mnt/FS_file232
loop233                       7:233  0   9.8M  0 loop  /mnt/FS_file233
loop234                       7:234  0   9.8M  0 loop  /mnt/FS_file234
loop235                       7:235  0   9.8M  0 loop  /mnt/FS_file235
loop236                       7:236  0   9.8M  0 loop  /mnt/FS_file236
loop237                       7:237  0   9.8M  0 loop  /mnt/FS_file237
loop238                       7:238  0   9.8M  0 loop  /mnt/FS_file238
loop239                       7:239  0   9.8M  0 loop  /mnt/FS_file239
loop240                       7:240  0   9.8M  0 loop  /mnt/FS_file240
loop241                       7:241  0   9.8M  0 loop  /mnt/FS_file241
loop242                       7:242  0   9.8M  0 loop  /mnt/FS_file242
loop243                       7:243  0   9.8M  0 loop  /mnt/FS_file243
loop244                       7:244  0   9.8M  0 loop  /mnt/FS_file244
loop245                       7:245  0   9.8M  0 loop  /mnt/FS_file245
loop246                       7:246  0   9.8M  0 loop  /mnt/FS_file246
loop247                       7:247  0   9.8M  0 loop  /mnt/FS_file247
loop248                       7:248  0   9.8M  0 loop  /mnt/FS_file248
loop249                       7:249  0   9.8M  0 loop  /mnt/FS_file249
loop250                       7:250  0   9.8M  0 loop  /mnt/FS_file250
loop251                       7:251  0   9.8M  0 loop  /mnt/FS_file251
loop252                       7:252  0   9.8M  0 loop  /mnt/FS_file252
loop253                       7:253  0   9.8M  0 loop  /mnt/FS_file253
loop254                       7:254  0   9.8M  0 loop  /mnt/FS_file254
loop255                       7:255  0   9.8M  0 loop  /mnt/FS_file255
loop256                       7:256  0   9.8M  0 loop  /mnt/FS_file256
loop257                       7:257  0   9.8M  0 loop  /mnt/FS_file257
loop258                       7:258  0   9.8M  0 loop  /mnt/FS_file258
loop259                       7:259  0   9.8M  0 loop  /mnt/FS_file259
loop260                       7:260  0   9.8M  0 loop  /mnt/FS_file260
loop261                       7:261  0   9.8M  0 loop  /mnt/FS_file261
loop262                       7:262  0   9.8M  0 loop  /mnt/FS_file262
loop263                       7:263  0   9.8M  0 loop  /mnt/FS_file263
loop264                       7:264  0   9.8M  0 loop  /mnt/FS_file264
loop265                       7:265  0   9.8M  0 loop  /mnt/FS_file265
loop266                       7:266  0   9.8M  0 loop  /mnt/FS_file266
loop267                       7:267  0   9.8M  0 loop  /mnt/FS_file267
loop268                       7:268  0   9.8M  0 loop  /mnt/FS_file268
loop269                       7:269  0   9.8M  0 loop  /mnt/FS_file269
loop270                       7:270  0   9.8M  0 loop  /mnt/FS_file270
loop271                       7:271  0   9.8M  0 loop  /mnt/FS_file271
loop272                       7:272  0   9.8M  0 loop  /mnt/FS_file272
loop273                       7:273  0   9.8M  0 loop  /mnt/FS_file273
loop274                       7:274  0   9.8M  0 loop  /mnt/FS_file274
loop275                       7:275  0   9.8M  0 loop  /mnt/FS_file275
loop276                       7:276  0   9.8M  0 loop  /mnt/FS_file276
loop277                       7:277  0   9.8M  0 loop  /mnt/FS_file277
loop278                       7:278  0   9.8M  0 loop  /mnt/FS_file278
loop279                       7:279  0   9.8M  0 loop  /mnt/FS_file279
loop280                       7:280  0   9.8M  0 loop  /mnt/FS_file280
loop281                       7:281  0   9.8M  0 loop  /mnt/FS_file281
loop282                       7:282  0   9.8M  0 loop  /mnt/FS_file282
loop283                       7:283  0   9.8M  0 loop  /mnt/FS_file283
loop284                       7:284  0   9.8M  0 loop  /mnt/FS_file284
loop285                       7:285  0   9.8M  0 loop  /mnt/FS_file285
loop286                       7:286  0   9.8M  0 loop  /mnt/FS_file286
loop287                       7:287  0   9.8M  0 loop  /mnt/FS_file287
loop288                       7:288  0   9.8M  0 loop  /mnt/FS_file288
loop289                       7:289  0   9.8M  0 loop  /mnt/FS_file289
loop290                       7:290  0   9.8M  0 loop  /mnt/FS_file290
loop291                       7:291  0   9.8M  0 loop  /mnt/FS_file291
loop292                       7:292  0   9.8M  0 loop  /mnt/FS_file292
loop293                       7:293  0   9.8M  0 loop  /mnt/FS_file293
loop294                       7:294  0   9.8M  0 loop  /mnt/FS_file294
loop295                       7:295  0   9.8M  0 loop  /mnt/FS_file295
loop296                       7:296  0   9.8M  0 loop  /mnt/FS_file296
loop297                       7:297  0   9.8M  0 loop  /mnt/FS_file297
loop298                       7:298  0   9.8M  0 loop  /mnt/FS_file298
loop299                       7:299  0   9.8M  0 loop  /mnt/FS_file299
loop10                        7:10   0   9.8M  0 loop  /mnt/FS_file10
loop11                        7:11   0   9.8M  0 loop  /mnt/FS_file11
loop12                        7:12   0   9.8M  0 loop  /mnt/FS_file12
loop13                        7:13   0   9.8M  0 loop  /mnt/FS_file13
loop14                        7:14   0   9.8M  0 loop  /mnt/FS_file14
loop15                        7:15   0   9.8M  0 loop  /mnt/FS_file15
loop16                        7:16   0   9.8M  0 loop  /mnt/FS_file16
loop17                        7:17   0   9.8M  0 loop  /mnt/FS_file17
loop18                        7:18   0   9.8M  0 loop  /mnt/FS_file18
loop19                        7:19   0   9.8M  0 loop  /mnt/FS_file19
loop20                        7:20   0   9.8M  0 loop  /mnt/FS_file20
loop21                        7:21   0   9.8M  0 loop  /mnt/FS_file21
loop22                        7:22   0   9.8M  0 loop  /mnt/FS_file22
loop23                        7:23   0   9.8M  0 loop  /mnt/FS_file23
loop24                        7:24   0   9.8M  0 loop  /mnt/FS_file24
loop25                        7:25   0   9.8M  0 loop  /mnt/FS_file25
loop26                        7:26   0   9.8M  0 loop  /mnt/FS_file26
loop27                        7:27   0   9.8M  0 loop  /mnt/FS_file27
loop28                        7:28   0   9.8M  0 loop  /mnt/FS_file28
loop29                        7:29   0   9.8M  0 loop  /mnt/FS_file29
loop30                        7:30   0   9.8M  0 loop  /mnt/FS_file30
loop31                        7:31   0   9.8M  0 loop  /mnt/FS_file31
loop32                        7:32   0   9.8M  0 loop  /mnt/FS_file32
loop33                        7:33   0   9.8M  0 loop  /mnt/FS_file33
loop34                        7:34   0   9.8M  0 loop  /mnt/FS_file34
loop35                        7:35   0   9.8M  0 loop  /mnt/FS_file35
loop36                        7:36   0   9.8M  0 loop  /mnt/FS_file36
loop37                        7:37   0   9.8M  0 loop  /mnt/FS_file37
loop38                        7:38   0   9.8M  0 loop  /mnt/FS_file38
loop39                        7:39   0   9.8M  0 loop  /mnt/FS_file39
loop40                        7:40   0   9.8M  0 loop  /mnt/FS_file40
loop41                        7:41   0   9.8M  0 loop  /mnt/FS_file41
loop42                        7:42   0   9.8M  0 loop  /mnt/FS_file42
loop43                        7:43   0   9.8M  0 loop  /mnt/FS_file43
loop44                        7:44   0   9.8M  0 loop  /mnt/FS_file44
loop45                        7:45   0   9.8M  0 loop  /mnt/FS_file45
loop46                        7:46   0   9.8M  0 loop  /mnt/FS_file46
loop47                        7:47   0   9.8M  0 loop  /mnt/FS_file47
loop48                        7:48   0   9.8M  0 loop  /mnt/FS_file48
loop49                        7:49   0   9.8M  0 loop  /mnt/FS_file49
loop50                        7:50   0   9.8M  0 loop  /mnt/FS_file50
loop51                        7:51   0   9.8M  0 loop  /mnt/FS_file51
loop52                        7:52   0   9.8M  0 loop  /mnt/FS_file52
loop53                        7:53   0   9.8M  0 loop  /mnt/FS_file53
loop54                        7:54   0   9.8M  0 loop  /mnt/FS_file54
loop55                        7:55   0   9.8M  0 loop  /mnt/FS_file55
loop56                        7:56   0   9.8M  0 loop  /mnt/FS_file56
loop57                        7:57   0   9.8M  0 loop  /mnt/FS_file57
loop58                        7:58   0   9.8M  0 loop  /mnt/FS_file58
loop59                        7:59   0   9.8M  0 loop  /mnt/FS_file59
loop60                        7:60   0   9.8M  0 loop  /mnt/FS_file60
loop61                        7:61   0   9.8M  0 loop  /mnt/FS_file61
loop62                        7:62   0   9.8M  0 loop  /mnt/FS_file62
loop63                        7:63   0   9.8M  0 loop  /mnt/FS_file63
loop64                        7:64   0   9.8M  0 loop  /mnt/FS_file64
loop65                        7:65   0   9.8M  0 loop  /mnt/FS_file65
loop66                        7:66   0   9.8M  0 loop  /mnt/FS_file66
loop67                        7:67   0   9.8M  0 loop  /mnt/FS_file67
loop68                        7:68   0   9.8M  0 loop  /mnt/FS_file68
loop69                        7:69   0   9.8M  0 loop  /mnt/FS_file69
loop70                        7:70   0   9.8M  0 loop  /mnt/FS_file70
loop71                        7:71   0   9.8M  0 loop  /mnt/FS_file71
loop72                        7:72   0   9.8M  0 loop  /mnt/FS_file72
loop73                        7:73   0   9.8M  0 loop  /mnt/FS_file73
loop74                        7:74   0   9.8M  0 loop  /mnt/FS_file74
loop75                        7:75   0   9.8M  0 loop  /mnt/FS_file75
loop76                        7:76   0   9.8M  0 loop  /mnt/FS_file76
loop77                        7:77   0   9.8M  0 loop  /mnt/FS_file77
loop78                        7:78   0   9.8M  0 loop  /mnt/FS_file78
loop79                        7:79   0   9.8M  0 loop  /mnt/FS_file79
loop80                        7:80   0   9.8M  0 loop  /mnt/FS_file80
loop81                        7:81   0   9.8M  0 loop  /mnt/FS_file81
loop82                        7:82   0   9.8M  0 loop  /mnt/FS_file82
loop83                        7:83   0   9.8M  0 loop  /mnt/FS_file83
loop84                        7:84   0   9.8M  0 loop  /mnt/FS_file84
loop85                        7:85   0   9.8M  0 loop  /mnt/FS_file85
loop86                        7:86   0   9.8M  0 loop  /mnt/FS_file86
loop87                        7:87   0   9.8M  0 loop  /mnt/FS_file87
loop88                        7:88   0   9.8M  0 loop  /mnt/FS_file88
loop89                        7:89   0   9.8M  0 loop  /mnt/FS_file89
loop90                        7:90   0   9.8M  0 loop  /mnt/FS_file90
loop91                        7:91   0   9.8M  0 loop  /mnt/FS_file91
loop92                        7:92   0   9.8M  0 loop  /mnt/FS_file92
loop93                        7:93   0   9.8M  0 loop  /mnt/FS_file93
loop94                        7:94   0   9.8M  0 loop  /mnt/FS_file94
loop95                        7:95   0   9.8M  0 loop  /mnt/FS_file95
loop96                        7:96   0   9.8M  0 loop  /mnt/FS_file96
loop97                        7:97   0   9.8M  0 loop  /mnt/FS_file97
loop98                        7:98   0   9.8M  0 loop  /mnt/FS_file98
loop99                        7:99   0   9.8M  0 loop  /mnt/FS_file99



create  partition using fdisk on /dev/loop299
磁盘 /dev/loop299：10 MB, 10240000 字节，20000 个扇区
Units = 扇区 of 1 * 512 = 512 bytes
扇区大小(逻辑/物理)：512 字节 / 512 字节
I/O 大小(最小/最佳)：512 字节 / 512 字节
磁盘标签类型：dos
磁盘标识符：0x18d3716b

        设备 Boot      Start         End      Blocks   Id  System
/dev/loop299p1            2048       19999        8976   83  Linux



[root@storageqe-06 ~]# kpartx -l FS_on_file299
mount: could not find any device /dev/loop#Bad address
can't set up loop
[root@storageqe-06 ~]# 
[root@storageqe-06 ~]# kpartx -a FS_on_file299
mount: could not find any device /dev/loop#Bad address
can't set up loop
[root@storageqe-06 ~]# kpartx -a /dev/loop299
device-mapper: reload ioctl on loop299p1  failed: Device or resource busy
create/reload failed on loop299p1



=============================================================================================================
Verified on device-mapper-multipath-0.4.9-133
[root@storageqe-06 ~]# rpm -qa | grep multipath
device-mapper-multipath-libs-0.4.9-133.el7.x86_64
device-mapper-multipath-0.4.9-133.el7.x86_64
[root@storageqe-06 ~]# 
[root@storageqe-06 ~]# rpm -qa | grep kpartx
kpartx-0.4.9-133.el7.x86_64


create 299 loop devices using below scripts. 
[root@storageqe-06 ~]# cat loop.sh 
for ((i=1;i<300;i++))
do
 dd if=/dev/zero of=FS_on_file$i bs=1k count=10000
   losetup /dev/loop$i FS_on_file$i
   mkfs -t ext3 /dev/loop$i
   mkdir /mnt/FS_file$i
   mount /dev/loop$i /mnt/FS_file$i
done 


[root@storageqe-06 ~]# lsblk
NAME                       MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                          8:0    0 136.7G  0 disk  
sdb                          8:16   0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                           253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                           253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                           253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                           253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                           253:8    0     2G  0 lvm   [SWAP]
sdc                          8:32   0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                           253:0    0     2G  0 mpath 
sdd                          8:48   0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                           253:3    0     2G  0 mpath 
sde                          8:64   0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                           253:1    0     2G  0 mpath 
sdf                          8:80   0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                           253:2    0     2G  0 mpath 
sdg                          8:96   0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                           253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                           253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                           253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                           253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                           253:8    0     2G  0 lvm   [SWAP]
sdh                          8:112  0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                           253:0    0     2G  0 mpath 
sdi                          8:128  0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                           253:3    0     2G  0 mpath 
sdj                          8:144  0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                           253:1    0     2G  0 mpath 
sdk                          8:160  0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                           253:2    0     2G  0 mpath 
sdl                          8:176  0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                           253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                           253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                           253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                           253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                           253:8    0     2G  0 lvm   [SWAP]
sdm                          8:192  0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                           253:0    0     2G  0 mpath 
sdn                          8:208  0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                           253:3    0     2G  0 mpath 
sdo                          8:224  0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                           253:1    0     2G  0 mpath 
sdp                          8:240  0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                           253:2    0     2G  0 mpath 
sdq                         65:0    0    20G  0 disk  
└─360a98000324669436c2b45666c56786d
                           253:4    0    20G  0 mpath 
  ├─360a98000324669436c2b45666c56786d1
                           253:5    0     1G  0 part  /boot
  └─360a98000324669436c2b45666c56786d2
                           253:6    0    19G  0 part  
    ├─rhel_storageqe--06-root
                           253:7    0    17G  0 lvm   /
    └─rhel_storageqe--06-swap
                           253:8    0     2G  0 lvm   [SWAP]
sdr                         65:16   0     2G  0 disk  
└─360a98000324669436c2b45666c56786f
                           253:0    0     2G  0 mpath 
sds                         65:32   0     2G  0 disk  
└─360a98000324669436c2b45666c567871
                           253:3    0     2G  0 mpath 
sdt                         65:48   0     2G  0 disk  
└─360a98000324669436c2b45666c567873
                           253:1    0     2G  0 mpath 
sdu                         65:64   0     2G  0 disk  
└─360a98000324669436c2b45666c567875
                           253:2    0     2G  0 mpath 
sr0                         11:0    1  1024M  0 rom   
loop0                        7:0    0   9.8M  0 loop  /mnt/FS_file1
loop1                        7:1    0   9.8M  0 loop  /mnt/FS_file1
loop2                        7:2    0   9.8M  0 loop  /mnt/FS_file2
loop3                        7:3    0   9.8M  0 loop  /mnt/FS_file3
loop4                        7:4    0   9.8M  0 loop  /mnt/FS_file4
loop5                        7:5    0   9.8M  0 loop  /mnt/FS_file5
loop6                        7:6    0   9.8M  0 loop  /mnt/FS_file6
loop7                        7:7    0   9.8M  0 loop  /mnt/FS_file7
loop8                        7:8    0   9.8M  0 loop  /mnt/FS_file8
loop9                        7:9    0   9.8M  0 loop  /mnt/FS_file9
loop100                      7:100  0   9.8M  0 loop  /mnt/FS_file100
loop101                      7:101  0   9.8M  0 loop  /mnt/FS_file101
loop102                      7:102  0   9.8M  0 loop  /mnt/FS_file102
loop103                      7:103  0   9.8M  0 loop  /mnt/FS_file103
loop104                      7:104  0   9.8M  0 loop  /mnt/FS_file104
loop105                      7:105  0   9.8M  0 loop  /mnt/FS_file105
loop106                      7:106  0   9.8M  0 loop  /mnt/FS_file106
loop107                      7:107  0   9.8M  0 loop  /mnt/FS_file107
loop108                      7:108  0   9.8M  0 loop  /mnt/FS_file108
loop109                      7:109  0   9.8M  0 loop  /mnt/FS_file109
loop110                      7:110  0   9.8M  0 loop  /mnt/FS_file110
loop111                      7:111  0   9.8M  0 loop  /mnt/FS_file111
loop112                      7:112  0   9.8M  0 loop  /mnt/FS_file112
loop113                      7:113  0   9.8M  0 loop  /mnt/FS_file113
loop114                      7:114  0   9.8M  0 loop  /mnt/FS_file114
loop115                      7:115  0   9.8M  0 loop  /mnt/FS_file115
loop116                      7:116  0   9.8M  0 loop  /mnt/FS_file116
loop117                      7:117  0   9.8M  0 loop  /mnt/FS_file117
loop118                      7:118  0   9.8M  0 loop  /mnt/FS_file118
loop119                      7:119  0   9.8M  0 loop  /mnt/FS_file119
loop120                      7:120  0   9.8M  0 loop  /mnt/FS_file120
loop121                      7:121  0   9.8M  0 loop  /mnt/FS_file121
loop122                      7:122  0   9.8M  0 loop  /mnt/FS_file122
loop123                      7:123  0   9.8M  0 loop  /mnt/FS_file123
loop124                      7:124  0   9.8M  0 loop  /mnt/FS_file124
loop125                      7:125  0   9.8M  0 loop  /mnt/FS_file125
loop126                      7:126  0   9.8M  0 loop  /mnt/FS_file126
loop127                      7:127  0   9.8M  0 loop  /mnt/FS_file127
loop128                      7:128  0   9.8M  0 loop  /mnt/FS_file128
loop129                      7:129  0   9.8M  0 loop  /mnt/FS_file129
loop130                      7:130  0   9.8M  0 loop  /mnt/FS_file130
loop131                      7:131  0   9.8M  0 loop  /mnt/FS_file131
loop132                      7:132  0   9.8M  0 loop  /mnt/FS_file132
loop133                      7:133  0   9.8M  0 loop  /mnt/FS_file133
loop134                      7:134  0   9.8M  0 loop  /mnt/FS_file134
loop135                      7:135  0   9.8M  0 loop  /mnt/FS_file135
loop136                      7:136  0   9.8M  0 loop  /mnt/FS_file136
loop137                      7:137  0   9.8M  0 loop  /mnt/FS_file137
loop138                      7:138  0   9.8M  0 loop  /mnt/FS_file138
loop139                      7:139  0   9.8M  0 loop  /mnt/FS_file139
loop140                      7:140  0   9.8M  0 loop  /mnt/FS_file140
loop141                      7:141  0   9.8M  0 loop  /mnt/FS_file141
loop142                      7:142  0   9.8M  0 loop  /mnt/FS_file142
loop143                      7:143  0   9.8M  0 loop  /mnt/FS_file143
loop144                      7:144  0   9.8M  0 loop  /mnt/FS_file144
loop145                      7:145  0   9.8M  0 loop  /mnt/FS_file145
loop146                      7:146  0   9.8M  0 loop  /mnt/FS_file146
loop147                      7:147  0   9.8M  0 loop  /mnt/FS_file147
loop148                      7:148  0   9.8M  0 loop  /mnt/FS_file148
loop149                      7:149  0   9.8M  0 loop  /mnt/FS_file149
loop150                      7:150  0   9.8M  0 loop  /mnt/FS_file150
loop151                      7:151  0   9.8M  0 loop  /mnt/FS_file151
loop152                      7:152  0   9.8M  0 loop  /mnt/FS_file152
loop153                      7:153  0   9.8M  0 loop  /mnt/FS_file153
loop154                      7:154  0   9.8M  0 loop  /mnt/FS_file154
loop155                      7:155  0   9.8M  0 loop  /mnt/FS_file155
loop156                      7:156  0   9.8M  0 loop  /mnt/FS_file156
loop157                      7:157  0   9.8M  0 loop  /mnt/FS_file157
loop158                      7:158  0   9.8M  0 loop  /mnt/FS_file158
loop159                      7:159  0   9.8M  0 loop  /mnt/FS_file159
loop160                      7:160  0   9.8M  0 loop  /mnt/FS_file160
loop161                      7:161  0   9.8M  0 loop  /mnt/FS_file161
loop162                      7:162  0   9.8M  0 loop  /mnt/FS_file162
loop163                      7:163  0   9.8M  0 loop  /mnt/FS_file163
loop164                      7:164  0   9.8M  0 loop  /mnt/FS_file164
loop165                      7:165  0   9.8M  0 loop  /mnt/FS_file165
loop166                      7:166  0   9.8M  0 loop  /mnt/FS_file166
loop167                      7:167  0   9.8M  0 loop  /mnt/FS_file167
loop168                      7:168  0   9.8M  0 loop  /mnt/FS_file168
loop169                      7:169  0   9.8M  0 loop  /mnt/FS_file169
loop170                      7:170  0   9.8M  0 loop  /mnt/FS_file170
loop171                      7:171  0   9.8M  0 loop  /mnt/FS_file171
loop172                      7:172  0   9.8M  0 loop  /mnt/FS_file172
loop173                      7:173  0   9.8M  0 loop  /mnt/FS_file173
loop174                      7:174  0   9.8M  0 loop  /mnt/FS_file174
loop175                      7:175  0   9.8M  0 loop  /mnt/FS_file175
loop176                      7:176  0   9.8M  0 loop  /mnt/FS_file176
loop177                      7:177  0   9.8M  0 loop  /mnt/FS_file177
loop178                      7:178  0   9.8M  0 loop  /mnt/FS_file178
loop179                      7:179  0   9.8M  0 loop  /mnt/FS_file179
loop180                      7:180  0   9.8M  0 loop  /mnt/FS_file180
loop181                      7:181  0   9.8M  0 loop  /mnt/FS_file181
loop182                      7:182  0   9.8M  0 loop  /mnt/FS_file182
loop183                      7:183  0   9.8M  0 loop  /mnt/FS_file183
loop184                      7:184  0   9.8M  0 loop  /mnt/FS_file184
loop185                      7:185  0   9.8M  0 loop  /mnt/FS_file185
loop186                      7:186  0   9.8M  0 loop  /mnt/FS_file186
loop187                      7:187  0   9.8M  0 loop  /mnt/FS_file187
loop188                      7:188  0   9.8M  0 loop  /mnt/FS_file188
loop189                      7:189  0   9.8M  0 loop  /mnt/FS_file189
loop190                      7:190  0   9.8M  0 loop  /mnt/FS_file190
loop191                      7:191  0   9.8M  0 loop  /mnt/FS_file191
loop192                      7:192  0   9.8M  0 loop  /mnt/FS_file192
loop193                      7:193  0   9.8M  0 loop  /mnt/FS_file193
loop194                      7:194  0   9.8M  0 loop  /mnt/FS_file194
loop195                      7:195  0   9.8M  0 loop  /mnt/FS_file195
loop196                      7:196  0   9.8M  0 loop  /mnt/FS_file196
loop197                      7:197  0   9.8M  0 loop  /mnt/FS_file197
loop198                      7:198  0   9.8M  0 loop  /mnt/FS_file198
loop199                      7:199  0   9.8M  0 loop  /mnt/FS_file199
loop200                      7:200  0   9.8M  0 loop  /mnt/FS_file200
loop201                      7:201  0   9.8M  0 loop  /mnt/FS_file201
loop202                      7:202  0   9.8M  0 loop  /mnt/FS_file202
loop203                      7:203  0   9.8M  0 loop  /mnt/FS_file203
loop204                      7:204  0   9.8M  0 loop  /mnt/FS_file204
loop205                      7:205  0   9.8M  0 loop  /mnt/FS_file205
loop206                      7:206  0   9.8M  0 loop  /mnt/FS_file206
loop207                      7:207  0   9.8M  0 loop  /mnt/FS_file207
loop208                      7:208  0   9.8M  0 loop  /mnt/FS_file208
loop209                      7:209  0   9.8M  0 loop  /mnt/FS_file209
loop210                      7:210  0   9.8M  0 loop  /mnt/FS_file210
loop211                      7:211  0   9.8M  0 loop  /mnt/FS_file211
loop212                      7:212  0   9.8M  0 loop  /mnt/FS_file212
loop213                      7:213  0   9.8M  0 loop  /mnt/FS_file213
loop214                      7:214  0   9.8M  0 loop  /mnt/FS_file214
loop215                      7:215  0   9.8M  0 loop  /mnt/FS_file215
loop216                      7:216  0   9.8M  0 loop  /mnt/FS_file216
loop217                      7:217  0   9.8M  0 loop  /mnt/FS_file217
loop218                      7:218  0   9.8M  0 loop  /mnt/FS_file218
loop219                      7:219  0   9.8M  0 loop  /mnt/FS_file219
loop220                      7:220  0   9.8M  0 loop  /mnt/FS_file220
loop221                      7:221  0   9.8M  0 loop  /mnt/FS_file221
loop222                      7:222  0   9.8M  0 loop  /mnt/FS_file222
loop223                      7:223  0   9.8M  0 loop  /mnt/FS_file223
loop224                      7:224  0   9.8M  0 loop  /mnt/FS_file224
loop225                      7:225  0   9.8M  0 loop  /mnt/FS_file225
loop226                      7:226  0   9.8M  0 loop  /mnt/FS_file226
loop227                      7:227  0   9.8M  0 loop  /mnt/FS_file227
loop228                      7:228  0   9.8M  0 loop  /mnt/FS_file228
loop229                      7:229  0   9.8M  0 loop  /mnt/FS_file229
loop230                      7:230  0   9.8M  0 loop  /mnt/FS_file230
loop231                      7:231  0   9.8M  0 loop  /mnt/FS_file231
loop232                      7:232  0   9.8M  0 loop  /mnt/FS_file232
loop233                      7:233  0   9.8M  0 loop  /mnt/FS_file233
loop234                      7:234  0   9.8M  0 loop  /mnt/FS_file234
loop235                      7:235  0   9.8M  0 loop  /mnt/FS_file235
loop236                      7:236  0   9.8M  0 loop  /mnt/FS_file236
loop237                      7:237  0   9.8M  0 loop  /mnt/FS_file237
loop238                      7:238  0   9.8M  0 loop  /mnt/FS_file238
loop239                      7:239  0   9.8M  0 loop  /mnt/FS_file239
loop240                      7:240  0   9.8M  0 loop  /mnt/FS_file240
loop241                      7:241  0   9.8M  0 loop  /mnt/FS_file241
loop242                      7:242  0   9.8M  0 loop  /mnt/FS_file242
loop243                      7:243  0   9.8M  0 loop  /mnt/FS_file243
loop244                      7:244  0   9.8M  0 loop  /mnt/FS_file244
loop245                      7:245  0   9.8M  0 loop  /mnt/FS_file245
loop246                      7:246  0   9.8M  0 loop  /mnt/FS_file246
loop247                      7:247  0   9.8M  0 loop  /mnt/FS_file247
loop248                      7:248  0   9.8M  0 loop  /mnt/FS_file248
loop249                      7:249  0   9.8M  0 loop  /mnt/FS_file249
loop250                      7:250  0   9.8M  0 loop  /mnt/FS_file250
loop251                      7:251  0   9.8M  0 loop  /mnt/FS_file251
loop252                      7:252  0   9.8M  0 loop  /mnt/FS_file252
loop253                      7:253  0   9.8M  0 loop  /mnt/FS_file253
loop254                      7:254  0   9.8M  0 loop  /mnt/FS_file254
loop255                      7:255  0   9.8M  0 loop  /mnt/FS_file255
loop256                      7:256  0   9.8M  0 loop  /mnt/FS_file256
loop257                      7:257  0   9.8M  0 loop  /mnt/FS_file257
loop258                      7:258  0   9.8M  0 loop  /mnt/FS_file258
loop259                      7:259  0   9.8M  0 loop  /mnt/FS_file259
loop260                      7:260  0   9.8M  0 loop  /mnt/FS_file260
loop261                      7:261  0   9.8M  0 loop  /mnt/FS_file261
loop262                      7:262  0   9.8M  0 loop  /mnt/FS_file262
loop263                      7:263  0   9.8M  0 loop  /mnt/FS_file263
loop264                      7:264  0   9.8M  0 loop  /mnt/FS_file264
loop265                      7:265  0   9.8M  0 loop  /mnt/FS_file265
loop266                      7:266  0   9.8M  0 loop  /mnt/FS_file266
loop267                      7:267  0   9.8M  0 loop  /mnt/FS_file267
loop268                      7:268  0   9.8M  0 loop  /mnt/FS_file268
loop269                      7:269  0   9.8M  0 loop  /mnt/FS_file269
loop270                      7:270  0   9.8M  0 loop  /mnt/FS_file270
loop271                      7:271  0   9.8M  0 loop  /mnt/FS_file271
loop272                      7:272  0   9.8M  0 loop  /mnt/FS_file272
loop273                      7:273  0   9.8M  0 loop  /mnt/FS_file273
loop274                      7:274  0   9.8M  0 loop  /mnt/FS_file274
loop275                      7:275  0   9.8M  0 loop  /mnt/FS_file275
loop276                      7:276  0   9.8M  0 loop  /mnt/FS_file276
loop277                      7:277  0   9.8M  0 loop  /mnt/FS_file277
loop278                      7:278  0   9.8M  0 loop  /mnt/FS_file278
loop279                      7:279  0   9.8M  0 loop  /mnt/FS_file279
loop280                      7:280  0   9.8M  0 loop  /mnt/FS_file280
loop281                      7:281  0   9.8M  0 loop  /mnt/FS_file281
loop282                      7:282  0   9.8M  0 loop  /mnt/FS_file282
loop283                      7:283  0   9.8M  0 loop  /mnt/FS_file283
loop284                      7:284  0   9.8M  0 loop  /mnt/FS_file284
loop285                      7:285  0   9.8M  0 loop  /mnt/FS_file285
loop286                      7:286  0   9.8M  0 loop  /mnt/FS_file286
loop287                      7:287  0   9.8M  0 loop  /mnt/FS_file287
loop288                      7:288  0   9.8M  0 loop  /mnt/FS_file288
loop289                      7:289  0   9.8M  0 loop  /mnt/FS_file289
loop290                      7:290  0   9.8M  0 loop  /mnt/FS_file290
loop291                      7:291  0   9.8M  0 loop  /mnt/FS_file291
loop292                      7:292  0   9.8M  0 loop  /mnt/FS_file292
loop293                      7:293  0   9.8M  0 loop  /mnt/FS_file293
loop294                      7:294  0   9.8M  0 loop  /mnt/FS_file294
loop295                      7:295  0   9.8M  0 loop  /mnt/FS_file295
loop296                      7:296  0   9.8M  0 loop  /mnt/FS_file296
loop297                      7:297  0   9.8M  0 loop  /mnt/FS_file297
loop298                      7:298  0   9.8M  0 loop  /mnt/FS_file298
loop299                      7:299  0   9.8M  0 loop  /mnt/FS_file299
loop10                       7:10   0   9.8M  0 loop  /mnt/FS_file10
loop11                       7:11   0   9.8M  0 loop  /mnt/FS_file11
loop12                       7:12   0   9.8M  0 loop  /mnt/FS_file12
loop13                       7:13   0   9.8M  0 loop  /mnt/FS_file13
loop14                       7:14   0   9.8M  0 loop  /mnt/FS_file14
loop15                       7:15   0   9.8M  0 loop  /mnt/FS_file15
loop16                       7:16   0   9.8M  0 loop  /mnt/FS_file16
loop17                       7:17   0   9.8M  0 loop  /mnt/FS_file17
loop18                       7:18   0   9.8M  0 loop  /mnt/FS_file18
loop19                       7:19   0   9.8M  0 loop  /mnt/FS_file19
loop20                       7:20   0   9.8M  0 loop  /mnt/FS_file20
loop21                       7:21   0   9.8M  0 loop  /mnt/FS_file21
loop22                       7:22   0   9.8M  0 loop  /mnt/FS_file22
loop23                       7:23   0   9.8M  0 loop  /mnt/FS_file23
loop24                       7:24   0   9.8M  0 loop  /mnt/FS_file24
loop25                       7:25   0   9.8M  0 loop  /mnt/FS_file25
loop26                       7:26   0   9.8M  0 loop  /mnt/FS_file26
loop27                       7:27   0   9.8M  0 loop  /mnt/FS_file27
loop28                       7:28   0   9.8M  0 loop  /mnt/FS_file28
loop29                       7:29   0   9.8M  0 loop  /mnt/FS_file29
loop30                       7:30   0   9.8M  0 loop  /mnt/FS_file30
loop31                       7:31   0   9.8M  0 loop  /mnt/FS_file31
loop32                       7:32   0   9.8M  0 loop  /mnt/FS_file32
loop33                       7:33   0   9.8M  0 loop  /mnt/FS_file33
loop34                       7:34   0   9.8M  0 loop  /mnt/FS_file34
loop35                       7:35   0   9.8M  0 loop  /mnt/FS_file35
loop36                       7:36   0   9.8M  0 loop  /mnt/FS_file36
loop37                       7:37   0   9.8M  0 loop  /mnt/FS_file37
loop38                       7:38   0   9.8M  0 loop  /mnt/FS_file38
loop39                       7:39   0   9.8M  0 loop  /mnt/FS_file39
loop40                       7:40   0   9.8M  0 loop  /mnt/FS_file40
loop41                       7:41   0   9.8M  0 loop  /mnt/FS_file41
loop42                       7:42   0   9.8M  0 loop  /mnt/FS_file42
loop43                       7:43   0   9.8M  0 loop  /mnt/FS_file43
loop44                       7:44   0   9.8M  0 loop  /mnt/FS_file44
loop45                       7:45   0   9.8M  0 loop  /mnt/FS_file45
loop46                       7:46   0   9.8M  0 loop  /mnt/FS_file46
loop47                       7:47   0   9.8M  0 loop  /mnt/FS_file47
loop48                       7:48   0   9.8M  0 loop  /mnt/FS_file48
loop49                       7:49   0   9.8M  0 loop  /mnt/FS_file49
loop50                       7:50   0   9.8M  0 loop  /mnt/FS_file50
loop51                       7:51   0   9.8M  0 loop  /mnt/FS_file51
loop52                       7:52   0   9.8M  0 loop  /mnt/FS_file52
loop53                       7:53   0   9.8M  0 loop  /mnt/FS_file53
loop54                       7:54   0   9.8M  0 loop  /mnt/FS_file54
loop55                       7:55   0   9.8M  0 loop  /mnt/FS_file55
loop56                       7:56   0   9.8M  0 loop  /mnt/FS_file56
loop57                       7:57   0   9.8M  0 loop  /mnt/FS_file57
loop58                       7:58   0   9.8M  0 loop  /mnt/FS_file58
loop59                       7:59   0   9.8M  0 loop  /mnt/FS_file59
loop60                       7:60   0   9.8M  0 loop  /mnt/FS_file60
loop61                       7:61   0   9.8M  0 loop  /mnt/FS_file61
loop62                       7:62   0   9.8M  0 loop  /mnt/FS_file62
loop63                       7:63   0   9.8M  0 loop  /mnt/FS_file63
loop64                       7:64   0   9.8M  0 loop  /mnt/FS_file64
loop65                       7:65   0   9.8M  0 loop  /mnt/FS_file65
loop66                       7:66   0   9.8M  0 loop  /mnt/FS_file66
loop67                       7:67   0   9.8M  0 loop  /mnt/FS_file67
loop68                       7:68   0   9.8M  0 loop  /mnt/FS_file68
loop69                       7:69   0   9.8M  0 loop  /mnt/FS_file69
loop70                       7:70   0   9.8M  0 loop  /mnt/FS_file70
loop71                       7:71   0   9.8M  0 loop  /mnt/FS_file71
loop72                       7:72   0   9.8M  0 loop  /mnt/FS_file72
loop73                       7:73   0   9.8M  0 loop  /mnt/FS_file73
loop74                       7:74   0   9.8M  0 loop  /mnt/FS_file74
loop75                       7:75   0   9.8M  0 loop  /mnt/FS_file75
loop76                       7:76   0   9.8M  0 loop  /mnt/FS_file76
loop77                       7:77   0   9.8M  0 loop  /mnt/FS_file77
loop78                       7:78   0   9.8M  0 loop  /mnt/FS_file78
loop79                       7:79   0   9.8M  0 loop  /mnt/FS_file79
loop80                       7:80   0   9.8M  0 loop  /mnt/FS_file80
loop81                       7:81   0   9.8M  0 loop  /mnt/FS_file81
loop82                       7:82   0   9.8M  0 loop  /mnt/FS_file82
loop83                       7:83   0   9.8M  0 loop  /mnt/FS_file83
loop84                       7:84   0   9.8M  0 loop  /mnt/FS_file84
loop85                       7:85   0   9.8M  0 loop  /mnt/FS_file85
loop86                       7:86   0   9.8M  0 loop  /mnt/FS_file86
loop87                       7:87   0   9.8M  0 loop  /mnt/FS_file87
loop88                       7:88   0   9.8M  0 loop  /mnt/FS_file88
loop89                       7:89   0   9.8M  0 loop  /mnt/FS_file89
loop90                       7:90   0   9.8M  0 loop  /mnt/FS_file90
loop91                       7:91   0   9.8M  0 loop  /mnt/FS_file91
loop92                       7:92   0   9.8M  0 loop  /mnt/FS_file92
loop93                       7:93   0   9.8M  0 loop  /mnt/FS_file93
loop94                       7:94   0   9.8M  0 loop  /mnt/FS_file94
loop95                       7:95   0   9.8M  0 loop  /mnt/FS_file95
loop96                       7:96   0   9.8M  0 loop  /mnt/FS_file96
loop97                       7:97   0   9.8M  0 loop  /mnt/FS_file97
loop98                       7:98   0   9.8M  0 loop  /mnt/FS_file98
loop99                       7:99   0   9.8M  0 loop  /mnt/FS_file99



create  partition using fdisk on /dev/loop299
磁盘 /dev/loop299：10 MB, 10240000 字节，20000 个扇区
Units = 扇区 of 1 * 512 = 512 bytes
扇区大小(逻辑/物理)：512 字节 / 512 字节
I/O 大小(最小/最佳)：512 字节 / 512 字节
磁盘标签类型：dos
磁盘标识符：0x18d3716b

        设备 Boot      Start         End      Blocks   Id  System
/dev/loop299p1            2048       19999        8976   83  Linux



[root@storageqe-06 ~]# kpartx -l FS_on_file299
loop300p1 : 0 17952 /dev/loop300 2048
loop deleted : /dev/loop300
[root@storageqe-06 ~]# 
[root@storageqe-06 ~]# kpartx -a FS_on_file299
[root@storageqe-06 ~]# echo $?
0
[root@storageqe-06 ~]# kpartx -a /dev/loop29
[root@storageqe-06 ~]# echo $?
0




Test result:kpartx now will look in sysfs to find the loop devices, and accept minor number larger than 255

Comment 12 errata-xmlrpc 2020-09-29 20:01:05 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (device-mapper-multipath bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:3942