• Tao Ma's avatar
    fs/direct-io.c: calculate fs_count correctly in get_more_blocks() · ae55e1aa
    Tao Ma authored
    In get_more_blocks(), we use dio_count to calcuate fs_count and do some
    tricky things to increase fs_count if dio_count isn't aligned.  But
    actually it still has some corner cases that can't be coverd.  See the
    following example:
    	dio_write foo -s 1024 -w 4096
    (direct write 4096 bytes at offset 1024).  The same goes if the offset
    isn't aligned to fs_blocksize.
    In this case, the old calculation counts fs_count to be 1, but actually we
    will write into 2 different blocks (if fs_blocksize=4096).  The old code
    just works, since it will call get_block twice (and may have to allocate
    and create extents twice for filesystems like ext4).  So we'd better call
    get_block just once with the proper fs_count.
    Signed-off-by: default avatarTao Ma <boyu.mt@taobao.com>
    Cc: "Theodore Ts'o" <tytso@mit.edu>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
direct-io.c 37.6 KB