[Bugs] [Bug 1665880] New: After the shard feature is enabled, the glfs_read will always return the length of the read buffer, no the actual length readed

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1665880

            Bug ID: 1665880
           Summary: After the shard feature is enabled, the glfs_read will
                    always return the length of the read buffer, no the
                    actual length readed
           Product: GlusterFS
           Version: mainline
            Status: NEW
         Component: sharding
          Assignee: bugs at gluster.org
          Reporter: xiubli at redhat.com
        QA Contact: bugs at gluster.org
                CC: bugs at gluster.org
  Target Milestone: ---
    Classification: Community



Description of problem:

When I was testing the gluster-block/tcmu-runner with the glsuterfs mainline
code, there will be a crash in gluster-block:

# journalctl -r
[...]
16878 Jan 14 17:42:16 rhel3 kernel: gluster-blockd[5209]: segfault at 0 ip
00007fc430c0ff81 sp 00007fc42bffc608 error 4 in
libc-2.17.so[7fc430aa1000+1c3000]                 
16879 Jan 14 17:42:16 rhel3 systemd: gluster-blockd.service: main process
exited, code=killed, status=11/SEGV
16880 Jan 14 17:42:16 rhel3 systemd: Unit gluster-blockd.service entered failed
state.
16881 Jan 14 17:42:16 rhel3 systemd: gluster-blockd.service failed.
[...]

This is because when reading and parsing the meta-data file and after EOF the
loop won't stop and keep reading and glfs_read returns none zero.



Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. Create one volume and enable the features.shard
2. Try to allocate one buffer large enough and make sure the buffer size is
larger than the actual file size.
3. len = glfs_read (gfd, buffer, sizeof(buffer)).

Actual results:
len will always equal to sizeof(buffer)

Expected results:
len < sizeof(buffer)

Additional info:

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