On 2011-08-31, at 12:49 PM, Allison Henderson wrote:

On 08/30/2011 05:31 PM, Andreas Dilger wrote:

quoted

On 2011-08-30, at 6:28 PM, Allison Henderson wrote:

quoted

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.

quoted

quoted

Signed-off-by: Allison Henderson<redacted>
---
: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

Cheers, Andreas