direct-io: don't read inode->i_blkbits multiple times
Since directio can work on a raw block device, and the block size of the
device can change under it, we need to do the same thing that
fs/buffer.c now does: read the block size a single time, using
ACCESS_ONCE().
Reading it multiple times can get different results, which will then
confuse the code because it actually encodes the i_blksize in
relationship to the underlying logical blocksize.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/direct-io.c b/fs/direct-io.c
index f86c720..cf5b44b 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -540,6 +540,7 @@
sector_t fs_endblk; /* Into file, in filesystem-sized blocks */
unsigned long fs_count; /* Number of filesystem-sized blocks */
int create;
+ unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
/*
* If there was a memory error and we've overwritten all the
@@ -554,7 +555,7 @@
fs_count = fs_endblk - fs_startblk + 1;
map_bh->b_state = 0;
- map_bh->b_size = fs_count << dio->inode->i_blkbits;
+ map_bh->b_size = fs_count << i_blkbits;
/*
* For writes inside i_size on a DIO_SKIP_HOLES filesystem we
@@ -1053,7 +1054,8 @@
int seg;
size_t size;
unsigned long addr;
- unsigned blkbits = inode->i_blkbits;
+ unsigned i_blkbits = ACCESS_ONCE(inode->i_blkbits);
+ unsigned blkbits = i_blkbits;
unsigned blocksize_mask = (1 << blkbits) - 1;
ssize_t retval = -EINVAL;
loff_t end = offset;
@@ -1149,7 +1151,7 @@
dio->inode = inode;
dio->rw = rw;
sdio.blkbits = blkbits;
- sdio.blkfactor = inode->i_blkbits - blkbits;
+ sdio.blkfactor = i_blkbits - blkbits;
sdio.block_in_file = offset >> blkbits;
sdio.get_block = get_block;