Patchwork ext4: Don't check io->flag when setting EXT4_STATE_DIO_UNWRITTEN inode state.

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Submitter Tao Ma
Date Sept. 14, 2011, 7:16 a.m.
Message ID <1315984587-5039-1-git-send-email-tm@tao.ma>
Download mbox | patch
Permalink /patch/114583/
State Accepted
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Comments

Tao Ma - Sept. 14, 2011, 7:16 a.m.
From: Tao Ma <boyu.mt@taobao.com>

When we want to convert the unitialized extent in direct write,
we can either do it in ext4_end_io_nolock(AIO case) or in
 ext4_ext_direct_IO(non AIO case) and EXT4_I(inode)->cur_aio_dio
is a guard for ext4_ext_map_blocks to find the right case.
In e9e3bcecf, we mistakenly change it by:
-			if (io)
+			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
 				io->flag = EXT4_IO_END_UNWRITTEN;
-			else
+				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
+			} else
 				ext4_set_inode_state(inode,
 						     EXT4_STATE_DIO_UNWRITTEN);

So now if we map 2 blocks, and the first one set the EXT_IO_END_UNWRITTEN, the
2nd mapping will set inode state because of the check for the flag. This is
wrong.

Cc: Eric Sandeen <sandeen@redhat.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
---
 fs/ext4/extents.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)
Eric Sandeen - Sept. 14, 2011, 5:06 p.m.
On 9/14/11 2:16 AM, Tao Ma wrote:
> From: Tao Ma <boyu.mt@taobao.com>
> 
> When we want to convert the unitialized extent in direct write,
> we can either do it in ext4_end_io_nolock(AIO case) or in
>  ext4_ext_direct_IO(non AIO case) and EXT4_I(inode)->cur_aio_dio
> is a guard for ext4_ext_map_blocks to find the right case.
> In e9e3bcecf, we mistakenly change it by:
> -			if (io)
> +			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
>  				io->flag = EXT4_IO_END_UNWRITTEN;
> -			else
> +				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +			} else
>  				ext4_set_inode_state(inode,
>  						     EXT4_STATE_DIO_UNWRITTEN);
> 
> So now if we map 2 blocks, and the first one set the EXT_IO_END_UNWRITTEN, the
> 2nd mapping will set inode state because of the check for the flag. This is
> wrong.

Argh, yes, I think you are right.  Pesky else clause.  :(

Do you have a testcase for this?  And what is the user-visible outcome of the error,
is it data corruption?

> Cc: Eric Sandeen <sandeen@redhat.com>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
> ---
>  fs/ext4/extents.c |   16 ++++++++++------
>  1 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 57cf568..8db6743 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3190,9 +3190,11 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
>  		 * that this IO needs to conversion to written when IO is
>  		 * completed
>  		 */
> -		if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
> -			io->flag = EXT4_IO_END_UNWRITTEN;
> -			atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +		if (io) {
> +			if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
> +				io->flag = EXT4_IO_END_UNWRITTEN;
> +				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +			}
>  		} else
>  			ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
>  		if (ext4_should_dioread_nolock(inode))
> @@ -3572,9 +3574,11 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>  		 * that we need to perform conversion when IO is done.
>  		 */
>  		if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
> -			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
> -				io->flag = EXT4_IO_END_UNWRITTEN;
> -				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +			if (io) {
> +				if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
> +					io->flag = EXT4_IO_END_UNWRITTEN;
> +					atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +				}
>  			} else
>  				ext4_set_inode_state(inode,
>  						     EXT4_STATE_DIO_UNWRITTEN);

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Tao Ma - Sept. 15, 2011, 2:24 a.m.
On 09/15/2011 01:06 AM, Eric Sandeen wrote:
> On 9/14/11 2:16 AM, Tao Ma wrote:
>> From: Tao Ma <boyu.mt@taobao.com>
>>
>> When we want to convert the unitialized extent in direct write,
>> we can either do it in ext4_end_io_nolock(AIO case) or in
>>  ext4_ext_direct_IO(non AIO case) and EXT4_I(inode)->cur_aio_dio
>> is a guard for ext4_ext_map_blocks to find the right case.
>> In e9e3bcecf, we mistakenly change it by:
>> -			if (io)
>> +			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
>>  				io->flag = EXT4_IO_END_UNWRITTEN;
>> -			else
>> +				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
>> +			} else
>>  				ext4_set_inode_state(inode,
>>  						     EXT4_STATE_DIO_UNWRITTEN);
>>
>> So now if we map 2 blocks, and the first one set the EXT_IO_END_UNWRITTEN, the
>> 2nd mapping will set inode state because of the check for the flag. This is
>> wrong.
> 
> Argh, yes, I think you are right.  Pesky else clause.  :(
> 
> Do you have a testcase for this?  And what is the user-visible outcome of the error,
> is it data corruption?
sure, a very simple case can expose this.

fallocate -o 0 -l 1048576 $MNT_DIR/b
aio_test $MNT_DIR/b 4096 4096
aio_test $MNT_DIR/b 0 12288

The 2nd aio test will set the inode state. Currently, at least from my
test, it doesn't cause any data corruption because we only check
EXT4_STATE_DIO_UNWRITTEN like this:
if (ret > 0 && ext4_test_inode_state(inode,
                                    EXT4_STATE_DIO_UNWRITTEN))
So only if __blockdev_direct_IO returns us ret > 0, we will test this
flag. But the inode will have this flag from then on. I am not sure
whether there are other places complaining of it.

But I think we need this fix, first to make it more readable(at least it
is a little bit hard for me to understand the old one ;) ) and second to
avoid any future possible bug.

Thanks
Tao


> 
>> Cc: Eric Sandeen <sandeen@redhat.com>
>> Cc: "Theodore Ts'o" <tytso@mit.edu>
>> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
>> ---
>>  fs/ext4/extents.c |   16 ++++++++++------
>>  1 files changed, 10 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 57cf568..8db6743 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -3190,9 +3190,11 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
>>  		 * that this IO needs to conversion to written when IO is
>>  		 * completed
>>  		 */
>> -		if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
>> -			io->flag = EXT4_IO_END_UNWRITTEN;
>> -			atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
>> +		if (io) {
>> +			if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
>> +				io->flag = EXT4_IO_END_UNWRITTEN;
>> +				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
>> +			}
>>  		} else
>>  			ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
>>  		if (ext4_should_dioread_nolock(inode))
>> @@ -3572,9 +3574,11 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>>  		 * that we need to perform conversion when IO is done.
>>  		 */
>>  		if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
>> -			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
>> -				io->flag = EXT4_IO_END_UNWRITTEN;
>> -				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
>> +			if (io) {
>> +				if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
>> +					io->flag = EXT4_IO_END_UNWRITTEN;
>> +					atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
>> +				}
>>  			} else
>>  				ext4_set_inode_state(inode,
>>  						     EXT4_STATE_DIO_UNWRITTEN);
> 

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Tao Ma - Oct. 26, 2011, 7:44 a.m.
On 09/14/2011 03:16 PM, Tao Ma wrote:
> From: Tao Ma <boyu.mt@taobao.com>
> 
> When we want to convert the unitialized extent in direct write,
> we can either do it in ext4_end_io_nolock(AIO case) or in
>  ext4_ext_direct_IO(non AIO case) and EXT4_I(inode)->cur_aio_dio
> is a guard for ext4_ext_map_blocks to find the right case.
> In e9e3bcecf, we mistakenly change it by:
> -			if (io)
> +			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
>  				io->flag = EXT4_IO_END_UNWRITTEN;
> -			else
> +				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +			} else
>  				ext4_set_inode_state(inode,
>  						     EXT4_STATE_DIO_UNWRITTEN);
> 
> So now if we map 2 blocks, and the first one set the EXT_IO_END_UNWRITTEN, the
> 2nd mapping will set inode state because of the check for the flag. This is
> wrong.
> 
> Cc: Eric Sandeen <sandeen@redhat.com>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
ping?
> ---
>  fs/ext4/extents.c |   16 ++++++++++------
>  1 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 57cf568..8db6743 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3190,9 +3190,11 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
>  		 * that this IO needs to conversion to written when IO is
>  		 * completed
>  		 */
> -		if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
> -			io->flag = EXT4_IO_END_UNWRITTEN;
> -			atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +		if (io) {
> +			if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
> +				io->flag = EXT4_IO_END_UNWRITTEN;
> +				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +			}
>  		} else
>  			ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
>  		if (ext4_should_dioread_nolock(inode))
> @@ -3572,9 +3574,11 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>  		 * that we need to perform conversion when IO is done.
>  		 */
>  		if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
> -			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
> -				io->flag = EXT4_IO_END_UNWRITTEN;
> -				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +			if (io) {
> +				if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
> +					io->flag = EXT4_IO_END_UNWRITTEN;
> +					atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
> +				}
>  			} else
>  				ext4_set_inode_state(inode,
>  						     EXT4_STATE_DIO_UNWRITTEN);

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Theodore Ts'o - Oct. 27, 2011, 8 a.m.
On Wed, Sep 14, 2011 at 03:16:27PM +0800, Tao Ma wrote:
> From: Tao Ma <boyu.mt@taobao.com>
> 
> When we want to convert the unitialized extent in direct write,
> we can either do it in ext4_end_io_nolock(AIO case) or in
>  ext4_ext_direct_IO(non AIO case) and EXT4_I(inode)->cur_aio_dio
> is a guard for ext4_ext_map_blocks to find the right case.

Applied, thanks.

						- Ted
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Patch

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 57cf568..8db6743 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3190,9 +3190,11 @@  ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
 		 * that this IO needs to conversion to written when IO is
 		 * completed
 		 */
-		if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
-			io->flag = EXT4_IO_END_UNWRITTEN;
-			atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
+		if (io) {
+			if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
+				io->flag = EXT4_IO_END_UNWRITTEN;
+				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
+			}
 		} else
 			ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
 		if (ext4_should_dioread_nolock(inode))
@@ -3572,9 +3574,11 @@  int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 		 * that we need to perform conversion when IO is done.
 		 */
 		if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
-			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
-				io->flag = EXT4_IO_END_UNWRITTEN;
-				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
+			if (io) {
+				if (!(io->flag & EXT4_IO_END_UNWRITTEN)) {
+					io->flag = EXT4_IO_END_UNWRITTEN;
+					atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
+				}
 			} else
 				ext4_set_inode_state(inode,
 						     EXT4_STATE_DIO_UNWRITTEN);