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@xxxxxxxxxxxxxxxxxx>
---
: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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