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Subject[PATCH] mm: fix blkdev size calculation in generic_write_checks
Currently block device size calculated regardless its
bd_block_size. This may result attempt to write outside
block device if i_size not aligned to bdev->bd_block_size
and result in EIO.

#### TEST_CASE_BEGIN
# fdisk -l /dev/sdc
Disk /dev/sdc: 36.7 GB, 36703918080 bytes
255 heads, 63 sectors/track, 4462 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdc1 * 1 254 2040223+ 83 Ldinux
/dev/sdc2 255 379 1004062+ 83 Linux
####
#### /dev/sdc2 size not aligned to 4K
#### at this time bd_block_size == 512 so generic_write_check
#### performed correctly
# dd if=/dev/zero of=/dev/sdc2 bs=1k count=7 seek=1004058
dd: writing `/dev/sdc2': No space left on device
5+0 records in
4+0 records out
#### this bdev contain ext4fs with blksize = 4K
# mount /dev/sdc2 /mnt/
#### after we mounted this bdev bd_block_size == fsblksize == 4K
#### the same write operation failed with EIO
# dd if=/dev/zero of=/dev/sdc2 bs=1k count=7 seek=1004058
dd: writing `/dev/sdc2': Input/output error
3+0 records in
2+0 records out
#### Attempt to write whole fsblock result write access outside
#### blkdevice and cause -EIO (returned by blkdev_get_block)
#### TEST_CASE_END
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
mm/filemap.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 2c8776b..a23ee8a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1867,9 +1867,11 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i
} else {
#ifdef CONFIG_BLOCK
loff_t isize;
+ unsigned int blksize;
if (bdev_read_only(I_BDEV(inode)))
return -EPERM;
- isize = i_size_read(inode);
+ blksize = block_size(I_BDEV(inode));
+ isize = i_size_read(inode) & ~(blksize - 1);
if (*pos >= isize) {
if (*count || *pos > isize)
return -ENOSPC;
--
1.5.2.2

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