[PATCH] direct-io: don't introduce another read of inode->i_blkbits

Commit 20ce44d545844 ("do_direct_IO: Use inode->i_blkbits to compute
block count to be cleaned") introduced a regression: if the block size
of the block device is changed while a direct I/O request is being
setup, it can result in a panic.  See commit ab73857e354ab ("direct-io:
don't read inode->i_blkbits multiple times") for the reasoning, and
commit b87570f5d3496 ("Fix a crash when block device is read and block
size is changed at the same time") for a more detailed problem
description and reproducer.

Fixes: 20ce44d545844
Signed-off-by: Jeff Moyer <redacted>

---
Chandan, can you please test this to ensure this still fixes your problem?

diff --git a/fs/direct-io.c b/fs/direct-io.c
index b20adf9..c87bae4 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c

@@ -905,8 +905,8 @@ static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
 static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
 			struct buffer_head *map_bh)
 {
-	const unsigned i_blkbits = dio->inode->i_blkbits;
 	const unsigned blkbits = sdio->blkbits;
+	const unsigned i_blkbits = blkbits + sdio->blkfactor;
 	int ret = 0;
 
 	while (sdio->block_in_file < sdio->final_block_in_request) {

On 01/09/2017 02:42 PM, Jeff Moyer wrote:

Commit 20ce44d545844 ("do_direct_IO: Use inode->i_blkbits to compute
block count to be cleaned") introduced a regression: if the block size
of the block device is changed while a direct I/O request is being
setup, it can result in a panic.  See commit ab73857e354ab ("direct-io:
don't read inode->i_blkbits multiple times") for the reasoning, and
commit b87570f5d3496 ("Fix a crash when block device is read and block
size is changed at the same time") for a more detailed problem
description and reproducer.

Fixes: 20ce44d545844
Signed-off-by: Jeff Moyer <redacted>

---
Chandan, can you please test this to ensure this still fixes your problem?

Please, that would be great. And if so, then let's fold the two.

-- 
Jens Axboe

On Monday, January 09, 2017 04:42:58 PM Jeff Moyer wrote:

Commit 20ce44d545844 ("do_direct_IO: Use inode->i_blkbits to compute
block count to be cleaned") introduced a regression: if the block size
of the block device is changed while a direct I/O request is being
setup, it can result in a panic.  See commit ab73857e354ab ("direct-io:
don't read inode->i_blkbits multiple times") for the reasoning, and
commit b87570f5d3496 ("Fix a crash when block device is read and block
size is changed at the same time") for a more detailed problem
description and reproducer.

Fixes: 20ce44d545844
Signed-off-by: Jeff Moyer <redacted>

---
Chandan, can you please test this to ensure this still fixes your problem?

This patch fixes the failure,

Tested-by: Chandan Rajendra <redacted>

-- 
chandan

On 01/09/2017 10:27 PM, Chandan Rajendra wrote:

On Monday, January 09, 2017 04:42:58 PM Jeff Moyer wrote:

quoted

Commit 20ce44d545844 ("do_direct_IO: Use inode->i_blkbits to compute
block count to be cleaned") introduced a regression: if the block size
of the block device is changed while a direct I/O request is being
setup, it can result in a panic.  See commit ab73857e354ab ("direct-io:
don't read inode->i_blkbits multiple times") for the reasoning, and
commit b87570f5d3496 ("Fix a crash when block device is read and block
size is changed at the same time") for a more detailed problem
description and reproducer.

Fixes: 20ce44d545844
Signed-off-by: Jeff Moyer <redacted>

---
Chandan, can you please test this to ensure this still fixes your problem?

This patch fixes the failure,

Tested-by: Chandan Rajendra <redacted>

I've updated the patch, thanks guys.

-- 
Jens Axboe