Bug 72242
| Summary: | O_DIRECT flag in open() syscall seems to be not working | ||
|---|---|---|---|
| Product: | [Retired] Red Hat Linux | Reporter: | Mindaugas Riauba <mindaugas> |
| Component: | kernel | Assignee: | Arjan van de Ven <arjanv> |
| Status: | CLOSED WORKSFORME | QA Contact: | Brian Brock <bbrock> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 7.3 | CC: | sct |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | i686 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2002-08-22 12:02:16 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
what filesystem is this on? Filesystems are ext2 and ext3. Program succeeds on /proc though. I just tried this on a 7.3 system, and it works fine for ext2 and fails on ext3, as expected --- ext3 does not yet support O_DIRECT. # mount /dev/cciss/c0d0p5 on / type ext3 (rw) none on /proc type proc (rw) usbdevfs on /proc/bus/usb type usbdevfs (rw) none on /dev/pts type devpts (rw,gid=5,mode=620) none on /dev/shm type tmpfs (rw) /dev/cciss/c0d0p6 on /var type ext3 (rw) /dev/cciss/c0d0p1 on /boot type ext2 (rw) # ./readtst /boot/vmlinuz-2.4.18-5smp Error reading file: Invalid argument Which kernel (uname -a), and what does "cat /proc/mounts" show? # uname -a Linux antares 2.4.18-5smp #1 SMP Mon Jun 10 15:19:40 EDT 2002 i686 unknown # cat /proc/mounts rootfs / rootfs rw 0 0 /dev/root / ext3 rw 0 0 /proc /proc proc rw 0 0 usbdevfs /proc/bus/usb usbdevfs rw 0 0 none /dev/pts devpts rw 0 0 none /dev/shm tmpfs rw 0 0 /dev/cciss/c0d0p6 /var ext3 rw 0 0 /dev/cciss/c0d0p1 /boot ext2 rw 0 0
My mistake. O_DIRECT produces errors only when trying to read not full block
files' endings.
And where to read more about programming with O_DIRECT? Which filesystems
supports it, what are the possible block sizes and so on.
[root@antares root]# mke2fs /dev/cciss/c0d0p2
mke2fs 1.27 (8-Mar-2002)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
256000 inodes, 511020 blocks
25551 blocks (5.00%) reserved for the super user
First data block=0
16 block groups
32768 blocks per group, 32768 fragments per group
16000 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 32 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
[root@antares root]# mount -t ext2 /dev/cciss/c0d0p2 /mnt/cdrom/
[root@antares root]# cd /mnt/cdrom/
[root@antares cdrom]# dd if=/dev/zero of=testing bs=8192 count=1024
1024+0 records in
1024+0 records out
[root@antares cdrom]# ~/readtst testing
OKOKOKOKOKOKOKOKOKOKOKOKOK<and so on>
[root@antares cdrom]# cp /boot/vmlinux-2.4.18-5smp .
[root@antares cdrom]# ~/readtst vmlinux-2.4.18-5smp
OKOKOKOKOKOKOKOKOK<.....>OKOKOKOKOKOKOKOKOKError reading file: Invalid argument
O_DIRECT _requires_ page size sized and aligned IO. Anything else is invalid by definition. |
From Bugzilla Helper: User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) Description of problem: I'm trying to use Direct I/O in my program by I'm not able to use O_DIRECT flag in open() syscall. Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: #include <sys/types.h> #include <sys/stat.h> #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #define O_DIRECT 040000 #define BUFSIZE 8192 int main (int argc, char **argv) { int fd, err; char *buf; if ( argc < 2 ) { printf ("Usage: readttst <filename>\n"); exit (1); } if ( (buf=valloc(BUFSIZE)) == NULL ) { printf ("Cannot allocate enough memory\n"); exit (4); } fd = open (argv[1], O_RDONLY | O_DIRECT); if ( fd == -1 ) { printf ("Cannot open file: %s. Error: %s\n", argv[1], strerror(errno)); exit (2); } if ( (err = read(fd, buf, BUFSIZE)) != 0 ) { if ( err == -1 ) { printf ("Error reading file: %s\n", strerror(errno)); exit (3); } printf ("OK"); } close (fd); return 0; } Actual Results: Program writes: Error reading file: Invalid argument Expected Results: I should get many "OK" messages. Additional info: