[Gluster-devel] The ctime of fstat is not correct which lead to "tar" utility error
Lian, George (NSB - CN/Hangzhou)
george.lian at nokia-sbell.com
Fri Jul 20 09:29:07 UTC 2018
Hi,
Sorry, there seems still have issue.
We use “dd” application of linux tools instead of my demo program, and if the file is not exist before dd, the issue still be there.
The test command is
rm -rf /mnt/test/file.txt ; dd if=/dev/zero of=/mnt/test/file.txt bs=512 count=1 oflag=sync;stat /mnt/test/file.txt;tar -czvf /tmp/abc.gz
1) If we set md-cache-timeout to 0, the issue will not happen
2) If we set md-cache-timeout to 1, the issue will 100% reproduced! (with new patch you mentioned in the mail)
Please see detail test result as the below:
bash-4.4# gluster v set export md-cache-timeout 0
volume set: failed: Volume export does not exist
bash-4.4# gluster v set test md-cache-timeout 0
volume set: success
bash-4.4# dd if=/dev/zero of=/mnt/test/file.txt bs=512 count=1 oflag=sync;stat /mnt/test/file.txt;tar -czvf /tmp/abc.gz /mnt/test/file.txt;stat /mnt/test/file.txt^C
bash-4.4# rm /mnt/test/file.txt
bash-4.4# dd if=/dev/zero of=/mnt/test/file.txt bs=512 count=1 oflag=sync;stat /mnt/test/file.txt;tar -czvf /tmp/abc.gz /mnt/test/file.txt;stat /mnt/test/file.txt
1+0 records in
1+0 records out
512 bytes copied, 0.00932571 s, 54.9 kB/s
File: /mnt/test/file.txt
Size: 512 Blocks: 1 IO Block: 131072 regular file
Device: 33h/51d Inode: 9949244856126716752 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2018-07-13 17:55:02.756000000 +0000
Modify: 2018-07-13 17:55:02.764000000 +0000
Change: 2018-07-13 17:55:02.768000000 +0000
Birth: -
tar: Removing leading `/' from member names
/mnt/test/file.txt
File: /mnt/test/file.txt
Size: 512 Blocks: 1 IO Block: 131072 regular file
Device: 33h/51d Inode: 9949244856126716752 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2018-07-13 17:55:02.776000000 +0000
Modify: 2018-07-13 17:55:02.764000000 +0000
Change: 2018-07-13 17:55:02.768000000 +0000
Birth: -
bash-4.4# gluster v set test md-cache-timeout 1
volume set: success
bash-4.4# rm /mnt/test/file.txt
bash-4.4# dd if=/dev/zero of=/mnt/test/file.txt bs=512 count=1 oflag=sync;stat /mnt/test/file.txt;tar -czvf /tmp/abc.gz /mnt/test/file.txt;stat /mnt/test/file.txt
1+0 records in
1+0 records out
512 bytes copied, 0.0107589 s, 47.6 kB/s
File: /mnt/test/file.txt
Size: 512 Blocks: 1 IO Block: 131072 regular file
Device: 33h/51d Inode: 13569976446871695205 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2018-07-13 17:55:11.548000000 +0000
Modify: 2018-07-13 17:55:11.560000000 +0000
Change: 2018-07-13 17:55:11.560000000 +0000
Birth: -
tar: Removing leading `/' from member names
/mnt/test/file.txt
tar: /mnt/test/file.txt: file changed as we read it
File: /mnt/test/file.txt
Size: 512 Blocks: 1 IO Block: 131072 regular file
Device: 33h/51d Inode: 13569976446871695205 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2018-07-13 17:55:11.580000000 +0000
Modify: 2018-07-13 17:55:11.560000000 +0000
Change: 2018-07-13 17:55:11.564000000 +0000
Birth: -
Best Regards,
George
From: gluster-devel-bounces at gluster.org [mailto:gluster-devel-bounces at gluster.org] On Behalf Of Raghavendra Gowdappa
Sent: Friday, July 20, 2018 4:01 PM
To: Lian, George (NSB - CN/Hangzhou) <george.lian at nokia-sbell.com>
Cc: Zhang, Bingxuan (NSB - CN/Hangzhou) <bingxuan.zhang at nokia-sbell.com>; Raghavendra G <raghavendra at gluster.com>; Gluster-devel at gluster.org
Subject: Re: [Gluster-devel] The ctime of fstat is not correct which lead to "tar" utility error
On Fri, Jul 20, 2018 at 1:22 PM, Lian, George (NSB - CN/Hangzhou) <george.lian at nokia-sbell.com<mailto:george.lian at nokia-sbell.com>> wrote:
>>>We recently identified an issue with stat-prefetch. Fix can be found at:
>>>https://review.gluster.org/#/c/20410/11
>>>Can you let us know whether this helps?
The patch can resolve this issue, I have verified in Gluster 4.2(master trunk branch) and Gluster 3.12.3!
Thanks we'll merge it.
Thanks & Best Regards,
George
From: gluster-devel-bounces at gluster.org<mailto:gluster-devel-bounces at gluster.org> [mailto:gluster-devel-bounces at gluster.org<mailto:gluster-devel-bounces at gluster.org>] On Behalf Of Raghavendra Gowdappa
Sent: Thursday, July 19, 2018 5:06 PM
To: Lian, George (NSB - CN/Hangzhou) <george.lian at nokia-sbell.com<mailto:george.lian at nokia-sbell.com>>
Cc: Zhang, Bingxuan (NSB - CN/Hangzhou) <bingxuan.zhang at nokia-sbell.com<mailto:bingxuan.zhang at nokia-sbell.com>>; Gluster-devel at gluster.org<mailto:Gluster-devel at gluster.org>; Raghavendra G <raghavendra at gluster.com<mailto:raghavendra at gluster.com>>
Subject: Re: [Gluster-devel] The ctime of fstat is not correct which lead to "tar" utility error
On Thu, Jul 19, 2018 at 2:29 PM, Lian, George (NSB - CN/Hangzhou) <george.lian at nokia-sbell.com<mailto:george.lian at nokia-sbell.com>> wrote:
Hi, Gluster Experts,
In glusterfs version 3.12.3, There seems a “fstat” issue for ctime after we use fsync,
We have a demo execute binary which write some data and then do fsync for this file, it named as “tt”,
Then run tar command right after “tt” command, it will always error with “tar: /mnt/test/file1.txt: file changed as we read it”
The command output is list as the below, the source code and volume info configuration attached FYI,
This issue will be 100% reproducible! (/mnt/test is mountpoint of glusterfs volume “test” , which the volume info is attached in mail)
------------------------------------------------------------------
./tt;tar -czvf /tmp/abc.gz /mnt/test/file1.txt
mtime:1531247107.272000000
ctime:1531247107.272000000
tar: Removing leading `/' from member names
/mnt/test/file1.txt
tar: /mnt/test/file1.txt: file changed as we read it
----------------------------------------------------------------------
After my investigation, the xattrop for changelog is later than the fsync response , this is mean:
In function “afr_fsync_cbk” will call afr_delayed_changelog_wake_resume (this, local->fd, stub);
In our case, it always a pending changelog , so glusterfs save the metadata information to stub, and handle pending changelog first,
But the changelog will also change the ctime, from the packet captured by tcpdump, the response packet of xattrop will not include the metadata information, and the wake_resume also not handle this metadata changed case.
So in this case, the metadata in mdc_cache is not right, and when cache is valid, the application will get WRONG metadata!
For verify my guess, if I change the configuration for this volume
“gluster v set test md-cache-timeout 0” or
“gluster v set export stat-prefetch off”
This issue will be GONE!
We recently identified an issue with stat-prefetch. Fix can be found at:
https://review.gluster.org/#/c/20410/11
Can you let us know whether this helps?
And I restore the configuration to default, which mean stat-prefetch is on and md-cache-timeout is 1 second,
I try invalidate the md-cache in source code as the below in function mdc_fync_cbk on md-cache.c
The issue also will be GONE!
So GLusterFS Experts,
Could you please verify this issue, and share your comments on my investigation?
And your finally solutions is highly appreciated!
Does the following fix you've posted solves the problem?
------------------------------------changes in function “mdc_fsync_cbk”
int
mdc_fsync_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
int32_t op_ret, int32_t op_errno,
struct iatt *prebuf, struct iatt *postbuf, dict_t *xdata)
{
mdc_local_t *local = NULL;
local = frame->local;
if (op_ret != 0)
goto out;
if (!local)
goto out;
mdc_inode_iatt_set_validate(this, local->fd->inode, prebuf, postbuf,
_gf_true);
/* new added for ctime issue*/
mdc_inode_iatt_invalidate(this, local->fd->inode);
/* new added end*/
out:
MDC_STACK_UNWIND (fsync, frame, op_ret, op_errno, prebuf, postbuf,
xdata);
return 0;
}
---------------------------------------------------------------------------------
Best Regards,
George
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