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9p: fix enodata when reading growing file

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Reading from a file that was just extended by a write, but the write had
not yet reached the server would return ENODATA as illustrated by this
command:
$ xfs_io -c 'open -ft test' -c 'w 4096 1000' -c 'r 0 1000'
wrote 1000/1000 bytes at offset 4096
1000.000000 bytes, 1 ops; 0.0001 sec (5.610 MiB/sec and 5882.3529 ops/sec)
pread: No data available

Fix this case by having netfs assume zeroes when reads from server come
short like AFS and CEPH do

Link: https://lkml.kernel.org/r/20220110111444.926753-1-asmadeus@codewreck.org
Cc: stable@vger.kernel.org
Fixes: eb497943fa21 ("9p: Convert to using the netfs helper lib to do reads and caching")
Co-authored-by: David Howells <dhowells@redhat.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Tested-by: David Howells <dhowells@redhat.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
This commit is contained in:
Dominique Martinet 2022-01-10 20:10:31 +09:00
parent 15e2721b19
commit 19d1c32652
1 changed files with 5 additions and 0 deletions
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5
fs/9p/vfs_addr.c
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@ -42,6 +42,11 @@ static void v9fs_req_issue_op(struct netfs_read_subrequest *subreq)
iov_iter_xarray(&to, READ, &rreq->mapping->i_pages, pos, len);
total = p9_client_read(fid, pos, &to, &err);
/* if we just extended the file size, any portion not in
* cache won't be on server and is zeroes */
__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
netfs_subreq_terminated(subreq, err ?: total, false);
}