9p: fix enodata when reading growing file

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/[email protected]
Cc: [email protected]
Fixes: eb497943fa21 ("9p: Convert to using the netfs helper lib to do reads and caching")
Co-authored-by: David Howells <[email protected]>
Reviewed-by: David Howells <[email protected]>
Tested-by: David Howells <[email protected]>
Signed-off-by: Dominique Martinet <[email protected]>

0 files changed, 0 insertions, 0 deletions