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@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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