[Bugs] [Bug 1751722] Gluster fuse mount crashed during truncate

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1751722

Nir Soffer <nsoffer at redhat.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |needinfo?(kdhananj at redhat.c
                   |                            |om)



--- Comment #10 from Nir Soffer <nsoffer at redhat.com> ---
(In reply to Krutika Dhananjay from comment #5)
> RCA:
> The size going negative is when two consecutive truncates on the
> __DIRECT_IO_TEST__ file (coming from open with O_TRUNC) happened in the
> following sequence:
> 
> 1. Size of the file at the beginning - 512b

Did you reproduce this with storage with sector size of 512 or 4096?

On 4k storage I don't think we can have such file, unless there is 
another bug in gluster.

What vdsm does is equivalent to:

out=$1

for bs in 1 512 4096; do
    if dd if=/dev/zero bs=$bs count=1 of=$out oflag=direct conv=fsync; then
        echo $bs
        exit 0
    fi
done

echo "cannot use direct I/O" > &2
exit 1

On storage that does not support direct I/O the result is:

$ sh detect-block-size.sh /tmp/foo
dd: failed to open '/tmp/foo': Invalid argument
dd: failed to open '/tmp/foo': Invalid argument
dd: failed to open '/tmp/foo': Invalid argument
cannot use direct I/O

$ ls -lht /tmp/foo 
-rw-rw-r--. 1 nsoffer nsoffer 0 Sep 19 19:46 /tmp/foo

On storage with sector size of 512:

$ sh detect-block-size.sh /var/tmp/foo
dd: error writing '/var/tmp/foo': Invalid argument
1+0 records in
0+0 records out
0 bytes copied, 0.000392325 s, 0.0 kB/s
1+0 records in
1+0 records out
512 bytes copied, 0.0601933 s, 8.5 kB/s
512

$ ls -lht /var/tmp/foo
-rw-rw-r--. 1 nsoffer nsoffer 512 Sep 19 19:48 /var/tmp/foo

On storage with sector size of 4096:

$ sh detect-block-size.sh /var/tmp/vdsm-storage/mount.mount-4k/foo
dd: error writing '/var/tmp/vdsm-storage/mount.mount-4k/foo': Invalid argument
1+0 records in
0+0 records out
0 bytes copied, 0.000116669 s, 0.0 kB/s
dd: error writing '/var/tmp/vdsm-storage/mount.mount-4k/foo': Invalid argument
1+0 records in
0+0 records out
0 bytes copied, 0.000115637 s, 0.0 kB/s
1+0 records in
1+0 records out
4096 bytes (4.1 kB, 4.0 KiB) copied, 0.00483159 s, 848 kB/s
4096

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