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| author | Tao Ma <boyu.mt@taobao.com> | 2012-01-12 17:20:33 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-01-12 20:13:12 -0800 |
| commit | ae55e1aaa7e2e57e538cb98cf617f511c5dc4f73 (patch) | |
| tree | 3f3981dd7617c656e7a6ba2f3a83a14637c63221 /fs/direct-io.c | |
| parent | 45dac90f0ca7d9efeda8f3d416c808c71207bf20 (diff) | |
| download | lwn-ae55e1aaa7e2e57e538cb98cf617f511c5dc4f73.tar.gz lwn-ae55e1aaa7e2e57e538cb98cf617f511c5dc4f73.zip | |
fs/direct-io.c: calculate fs_count correctly in get_more_blocks()
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: Tao 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/direct-io.c')
| -rw-r--r-- | fs/direct-io.c | 11 |
1 files changed, 4 insertions, 7 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c index d740ab67ff6e..389863f59cda 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -580,9 +580,8 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, { int ret; sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ + sector_t fs_endblk; /* Into file, in filesystem-sized blocks */ unsigned long fs_count; /* Number of filesystem-sized blocks */ - unsigned long dio_count;/* Number of dio_block-sized blocks */ - unsigned long blkmask; int create; /* @@ -593,11 +592,9 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, if (ret == 0) { BUG_ON(sdio->block_in_file >= sdio->final_block_in_request); fs_startblk = sdio->block_in_file >> sdio->blkfactor; - dio_count = sdio->final_block_in_request - sdio->block_in_file; - fs_count = dio_count >> sdio->blkfactor; - blkmask = (1 << sdio->blkfactor) - 1; - if (dio_count & blkmask) - fs_count++; + fs_endblk = (sdio->final_block_in_request - 1) >> + sdio->blkfactor; + fs_count = fs_endblk - fs_startblk + 1; map_bh->b_state = 0; map_bh->b_size = fs_count << dio->inode->i_blkbits; |