Bug 1470157
| Summary: | symbolic links are broken | ||||||
|---|---|---|---|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Richard W.M. Jones <rjones> | ||||
| Component: | supermin | Assignee: | Richard W.M. Jones <rjones> | ||||
| Status: | CLOSED ERRATA | QA Contact: | Fedora Extras Quality Assurance <extras-qa> | ||||
| Severity: | unspecified | Docs Contact: | |||||
| Priority: | unspecified | ||||||
| Version: | rawhide | CC: | dhill, eguan, gansalmon, ichavero, itamar, jonathan, kernel-maint, labbott, madhu.chinakonda, mathieu.tarral, mchehab, pabeni, ptoscano, rjones | ||||
| Target Milestone: | --- | ||||||
| Target Release: | --- | ||||||
| Hardware: | Unspecified | ||||||
| OS: | Unspecified | ||||||
| Whiteboard: | |||||||
| Fixed In Version: | supermin-5.1.18-1.fc26 supermin-5.1.18-1.fc25 | Doc Type: | If docs needed, set a value | ||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | 2017-07-28 17:19:07 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: | |||||||
| Bug Depends On: | |||||||
| Bug Blocks: | 910269, 1494859 | ||||||
| Attachments: |
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Description
Richard W.M. Jones
2017-07-12 13:10:08 UTC
Created attachment 1296975 [details]
log from libguestfs-test-tool
Also broken in kernel-4.13.0-0.rc0.git5.1.fc27.x86_64 This is reproducible with the current upstream kernel, but not with v4.12 tag. Am currently bisecting ... 407cd7fb83c0ebabb490190e673d8c71ee7df97e is the first bad commit
commit 407cd7fb83c0ebabb490190e673d8c71ee7df97e
Author: Tahsin Erdogan <tahsin>
Date: Tue Jul 4 00:11:21 2017 -0400
ext4: change fast symlink test to not rely on i_blocks
ext4_inode_info->i_data is the storage area for 4 types of data:
a) Extents data
b) Inline data
c) Block map
d) Fast symlink data (symlink length < 60)
Extents data case is positively identified by EXT4_INODE_EXTENTS flag.
Inline data case is also obvious because of EXT4_INODE_INLINE_DATA
flag.
Distinguishing c) and d) however requires additional logic. This
currently relies on i_blocks count. After subtracting external xattr
block from i_blocks, if it is greater than 0 then we know that some
data blocks exist, so there must be a block map.
This logic got broken after ea_inode feature was added. That feature
charges the data blocks of external xattr inodes to the referencing
inode and so adds them to the i_blocks. To fix this, we could subtract
ea_inode blocks by iterating through all xattr entries and then check
whether remaining i_blocks count is zero. Besides being complicated,
this won't change the fact that the current way of distinguishing
between c) and d) is fragile.
The alternative solution is to test whether i_size is less than 60 to
determine fast symlink case. ext4_symlink() uses the same test to decide
whether to store the symlink in i_data. There is one caveat to address
before this can work though.
If an inode's i_nlink is zero during eviction, its i_size is set to
zero and its data is truncated. If system crashes before inode is removed
from the orphan list, next boot orphan cleanup may find the inode with
zero i_size. So, a symlink that had its data stored in a block may now
appear to be a fast symlink. The solution used in this patch is to treat
i_size = 0 as a non-fast symlink case. A zero sized symlink is not legal
so the only time this can happen is the mentioned scenario. This is also
logically correct because a i_size = 0 symlink has no data stored in
i_data.
Suggested-by: Andreas Dilger <adilger>
Signed-off-by: Tahsin Erdogan <tahsin>
Signed-off-by: Theodore Ts'o <tytso>
Reviewed-by: Andreas Dilger <adilger>
:040000 040000 31b0eecd7314c483ed78346637ebb6a85c49741b 47a1dbadb0203d7f7d233224d47c5889ab22fc4f M fs
Thanks for the bisect! I haven't seen this reported on the ext4 mailing list so your best bet is to e-mail that list directly. Actually I think I'm going to blame supermin for creating fast symlinks wrong. For the full explanation see: https://www.redhat.com/archives/libguestfs/2017-July/msg00078.html It's an open question if the kernel wants to support the "fast symlinks stored slow" or if that is considered to be an erroneous filesystem. *** Bug 1470375 has been marked as a duplicate of this bug. *** How can I tell supermin to use 4.12 kernel? (In reply to David Hill from comment #8) > How can I tell supermin to use 4.12 kernel? export SUPERMIN_KERNEL=/path/to/linux.git/arch/x86/boot/bzImage export SUPERMIN_MODULES=/tmp/kmods/lib/modules/3.xx.yy I've tried using the previous 4.11.0-1 kernel and it worked as previously. (In reply to David Hill from comment #9) > (In reply to David Hill from comment #8) > > How can I tell supermin to use 4.12 kernel? > > export SUPERMIN_KERNEL=/path/to/linux.git/arch/x86/boot/bzImage > export SUPERMIN_MODULES=/tmp/kmods/lib/modules/3.xx.yy export SUPERMIN_KERNEL=/boot/vmlinuz-4.11.6-300.fc26.x86_64 export SUPERMIN_MODULES=/lib/modules/4.11.6-300.fc26.x86_64 rm -rf /var/tmp/.guestfs-* Upstream discussion of the kernel/ext4 issues: https://marc.info/?l=linux-ext4&m=149987925520576&w=2 Click ‘Subject: Fast symlinks stored slow’ to see the full thread. supermin-5.1.18-1.fc26 has been submitted as an update to Fedora 26. https://bodhi.fedoraproject.org/updates/FEDORA-2017-f6b14e0e63 supermin-5.1.18-1.fc25 has been submitted as an update to Fedora 25. https://bodhi.fedoraproject.org/updates/FEDORA-2017-e587cfd70e (In reply to David Hill from comment #10) > I've tried using the previous 4.11.0-1 kernel and it worked as previously. There are new supermin builds for Fedora 25, 26 and Rawhide, please see if one of those works with the latest kernel: https://koji.fedoraproject.org/koji/packageinfo?packageID=15420 This looks promising. I've removed my exports and retried and it booted. I'll try another build that I didn't modify and come back later on today. supermin-5.1.18-1.fc25 has been pushed to the Fedora 25 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2017-e587cfd70e supermin-5.1.18-1.fc26 has been pushed to the Fedora 26 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2017-f6b14e0e63 supermin-5.1.18-1.fc26 has been pushed to the Fedora 26 stable repository. If problems still persist, please make note of it in this bug report. supermin-5.1.18-1.fc25 has been pushed to the Fedora 25 stable repository. If problems still persist, please make note of it in this bug report. If you are looking for an update supermin5 package for RHEL 7, see: https://www.redhat.com/archives/libguestfs/2017-November/msg00006.html "Libguestfs for RHEL 7.5 preview repository" *** Bug 1534616 has been marked as a duplicate of this bug. *** |