From: Tao Ma <boyu.mt@xxxxxxxxxx>
In get_more_blocks, we use dio_count to calculate fs_count and do some
tricky things to increase fs_count if dio_count isn't aligned. But
actually it still has some cornor case 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 extent twice for file systems like ext4). So we'd better call
get_block just once with the proper fs_count.
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Tao Ma <boyu.mt@xxxxxxxxxx>
---
Christoph, this is the updated version. I have done some tests against it and
it works. And the only difference between the old and this one is the change
from dio to sdio. Thanks.
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 d740ab6..5582183 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;
--
1.7.1
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