• Eryu Guan's avatar
    xfs: fix off-by-one on max nr_pages in xfs_find_get_desired_pgoff() · 59acce81
    Eryu Guan authored
    [ Upstream commit 8affebe1 ]
    
    xfs_find_get_desired_pgoff() is used to search for offset of hole or
    data in page range [index, end] (both inclusive), and the max number
    of pages to search should be at least one, if end == index.
    Otherwise the only page is missed and no hole or data is found,
    which is not correct.
    
    When block size is smaller than page size, this can be demonstrated
    by preallocating a file with size smaller than page size and writing
    data to the last block. E.g. run this xfs_io command on a 1k block
    size XFS on x86_64 host.
    
      # xfs_io -fc "falloc 0 3k" -c "pwrite 2k 1k" \
      	    -c "seek -d 0" /mnt/xfs/testfile
      wrote 1024/1024 bytes at offset 2048
      1 KiB, 1 ops; 0.0000 sec (33.675 MiB/sec and 34482.7586 ops/sec)
      Whence  Result
      DATA    EOF
    
    Data at offset 2k was missed, and lseek(2) returned ENXIO.
    
    This is uncovered by generic/285 subtest 07 and 08 on ppc64 host,
    where pagesize is 64k. Because a recent change to generic/285
    reduced the preallocated file size to smaller than 64k.
    
    Cc: stable@vger.kernel.org # v3.7+
    Signed-off-by: default avatarEryu Guan <eguan@redhat.com>
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
    59acce81
xfs_file.c 39.3 KB