Patchwork [4/6,v7] ext4: Lock i_mutex for punch hole

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Submitter Allison Henderson
Date Aug. 31, 2011, 12:28 a.m.
Message ID <1314750513-10045-5-git-send-email-achender@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/112402/
State Rejected
Headers show

Comments

Allison Henderson - Aug. 31, 2011, 12:28 a.m.
This patch modifies the fallocate routine to lock i_mutex during
the punch hole operation.

Yongqiang noticed that the vfs layer locks i_mutex for truncate,
but not fallocate, so the fallocate routine will need to take
care of locking i_mutex.  Otherwise a page may be mapped after
punch hole has released the pages, but before i_data_sem is
locked to release the blocks in the extent tree.

Signed-off-by: Allison Henderson <achender@linux.vnet.ibm.com>
---
:100644 100644 9124cd2... 007fb08... M	fs/ext4/extents.c
 fs/ext4/extents.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)
Andreas Dilger - Aug. 31, 2011, 12:31 a.m.
On 2011-08-30, at 6:28 PM, Allison Henderson wrote:
> This patch modifies the fallocate routine to lock i_mutex during
> the punch hole operation.
> 
> Yongqiang noticed that the vfs layer locks i_mutex for truncate,
> but not fallocate, so the fallocate routine will need to take
> care of locking i_mutex.  Otherwise a page may be mapped after
> punch hole has released the pages, but before i_data_sem is
> locked to release the blocks in the extent tree.

If the VFS is locking i_mutex for truncate, shouldn't the locking for
fallocate() also be done in the VFS?

> Signed-off-by: Allison Henderson <achender@linux.vnet.ibm.com>
> ---
> :100644 100644 9124cd2... 007fb08... M	fs/ext4/extents.c
> fs/ext4/extents.c |   10 +++++++---
> 1 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 9124cd2..007fb08 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3774,8 +3774,13 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
> 		return -EOPNOTSUPP;
> 
> -	if (mode & FALLOC_FL_PUNCH_HOLE)
> -		return ext4_punch_hole(file, offset, len);
> +	mutex_lock(&inode->i_mutex);
> +
> +	if (mode & FALLOC_FL_PUNCH_HOLE) {
> +		ret = ext4_punch_hole(file, offset, len);
> +		mutex_unlock(&inode->i_mutex);
> +		return ret;	
> +	}
> 
> 	trace_ext4_fallocate_enter(inode, offset, len, mode);
> 	map.m_lblk = offset >> blkbits;
> @@ -3789,7 +3794,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> 	 * credits to insert 1 extent into extent tree
> 	 */
> 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
> -	mutex_lock(&inode->i_mutex);
> 	ret = inode_newsize_ok(inode, (len + offset));
> 	if (ret) {
> 		mutex_unlock(&inode->i_mutex);
> -- 
> 1.7.1
> 
> --
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Cheers, Andreas





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Allison Henderson - Aug. 31, 2011, 6:49 p.m.
On 08/30/2011 05:31 PM, Andreas Dilger wrote:
> On 2011-08-30, at 6:28 PM, Allison Henderson wrote:
>> This patch modifies the fallocate routine to lock i_mutex during
>> the punch hole operation.
>>
>> Yongqiang noticed that the vfs layer locks i_mutex for truncate,
>> but not fallocate, so the fallocate routine will need to take
>> care of locking i_mutex.  Otherwise a page may be mapped after
>> punch hole has released the pages, but before i_data_sem is
>> locked to release the blocks in the extent tree.
>
> If the VFS is locking i_mutex for truncate, shouldn't the locking for
> fallocate() also be done in the VFS?

Alrighty, I will do some poking around with this idea first.  I dont 
know if other files systems are already locking i_mutex during 
fallocate, and it may be the case that not all filesystems need i_mutex 
locked for fallocate.  So I'll do a little research first, but I will 
post back with what I find.  Thx!

Allison Henderson

>
>> Signed-off-by: Allison Henderson<achender@linux.vnet.ibm.com>
>> ---
>> :100644 100644 9124cd2... 007fb08... M	fs/ext4/extents.c
>> fs/ext4/extents.c |   10 +++++++---
>> 1 files changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 9124cd2..007fb08 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -3774,8 +3774,13 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>> 	if (mode&  ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
>> 		return -EOPNOTSUPP;
>>
>> -	if (mode&  FALLOC_FL_PUNCH_HOLE)
>> -		return ext4_punch_hole(file, offset, len);
>> +	mutex_lock(&inode->i_mutex);
>> +
>> +	if (mode&  FALLOC_FL_PUNCH_HOLE) {
>> +		ret = ext4_punch_hole(file, offset, len);
>> +		mutex_unlock(&inode->i_mutex);
>> +		return ret;	
>> +	}
>>
>> 	trace_ext4_fallocate_enter(inode, offset, len, mode);
>> 	map.m_lblk = offset>>  blkbits;
>> @@ -3789,7 +3794,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>> 	 * credits to insert 1 extent into extent tree
>> 	 */
>> 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
>> -	mutex_lock(&inode->i_mutex);
>> 	ret = inode_newsize_ok(inode, (len + offset));
>> 	if (ret) {
>> 		mutex_unlock(&inode->i_mutex);
>> --
>> 1.7.1
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
> Cheers, Andreas
>
>
>
>
>

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Andreas Dilger - Aug. 31, 2011, 7:44 p.m.
On 2011-08-31, at 12:49 PM, Allison Henderson wrote:
> On 08/30/2011 05:31 PM, Andreas Dilger wrote:
>> On 2011-08-30, at 6:28 PM, Allison Henderson wrote:
>>> This patch modifies the fallocate routine to lock i_mutex during
>>> the punch hole operation.
>>> 
>>> Yongqiang noticed that the vfs layer locks i_mutex for truncate,
>>> but not fallocate, so the fallocate routine will need to take
>>> care of locking i_mutex.  Otherwise a page may be mapped after
>>> punch hole has released the pages, but before i_data_sem is
>>> locked to release the blocks in the extent tree.
>> 
>> If the VFS is locking i_mutex for truncate, shouldn't the locking for
>> fallocate() also be done in the VFS?
> 
> Alrighty, I will do some poking around with this idea first.  I dont know if other files systems are already locking i_mutex during fallocate, and it may be the case that not all filesystems need i_mutex locked for fallocate.  So I'll do a little research first, but I will post back with what I find.  Thx!

Probably a good idea to bring up this issue on linux-fsdevel.

>>> Signed-off-by: Allison Henderson<achender@linux.vnet.ibm.com>
>>> ---
>>> :100644 100644 9124cd2... 007fb08... M	fs/ext4/extents.c
>>> fs/ext4/extents.c |   10 +++++++---
>>> 1 files changed, 7 insertions(+), 3 deletions(-)
>>> 
>>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>>> index 9124cd2..007fb08 100644
>>> --- a/fs/ext4/extents.c
>>> +++ b/fs/ext4/extents.c
>>> @@ -3774,8 +3774,13 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>>> 	if (mode&  ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
>>> 		return -EOPNOTSUPP;
>>> 
>>> -	if (mode&  FALLOC_FL_PUNCH_HOLE)
>>> -		return ext4_punch_hole(file, offset, len);
>>> +	mutex_lock(&inode->i_mutex);
>>> +
>>> +	if (mode&  FALLOC_FL_PUNCH_HOLE) {
>>> +		ret = ext4_punch_hole(file, offset, len);
>>> +		mutex_unlock(&inode->i_mutex);
>>> +		return ret;	
>>> +	}
>>> 
>>> 	trace_ext4_fallocate_enter(inode, offset, len, mode);
>>> 	map.m_lblk = offset>>  blkbits;
>>> @@ -3789,7 +3794,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>>> 	 * credits to insert 1 extent into extent tree
>>> 	 */
>>> 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
>>> -	mutex_lock(&inode->i_mutex);
>>> 	ret = inode_newsize_ok(inode, (len + offset));
>>> 	if (ret) {
>>> 		mutex_unlock(&inode->i_mutex);
>>> --
>>> 1.7.1
>>> 
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> 
>> 
>> Cheers, Andreas
>> 
>> 
>> 
>> 
>> 
> 


Cheers, Andreas





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Patch

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 9124cd2..007fb08 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3774,8 +3774,13 @@  long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 		return -EOPNOTSUPP;
 
-	if (mode & FALLOC_FL_PUNCH_HOLE)
-		return ext4_punch_hole(file, offset, len);
+	mutex_lock(&inode->i_mutex);
+
+	if (mode & FALLOC_FL_PUNCH_HOLE) {
+		ret = ext4_punch_hole(file, offset, len);
+		mutex_unlock(&inode->i_mutex);
+		return ret;	
+	}
 
 	trace_ext4_fallocate_enter(inode, offset, len, mode);
 	map.m_lblk = offset >> blkbits;
@@ -3789,7 +3794,6 @@  long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	 * credits to insert 1 extent into extent tree
 	 */
 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
-	mutex_lock(&inode->i_mutex);
 	ret = inode_newsize_ok(inode, (len + offset));
 	if (ret) {
 		mutex_unlock(&inode->i_mutex);