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authorMiklos Szeredi <mszeredi@suse.cz>2009-04-06 17:41:00 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-07 08:34:46 -0700
commit7bfac9ecf0585962fe13584f5cf526d8c8e76f17 (patch)
tree7e7c98311bb0d4c26e514b337216bbc8ade8d078 /fs/ocfs2
parent612392307cb09e49051225092cbbd7049bd8db93 (diff)
splice: fix deadlock in splicing to file
There's a possible deadlock in generic_file_splice_write(), splice_from_pipe() and ocfs2_file_splice_write(): - task A calls generic_file_splice_write() - this calls inode_double_lock(), which locks i_mutex on both pipe->inode and target inode - ordering depends on inode pointers, can happen that pipe->inode is locked first - __splice_from_pipe() needs more data, calls pipe_wait() - this releases lock on pipe->inode, goes to interruptible sleep - task B calls generic_file_splice_write(), similarly to the first - this locks pipe->inode, then tries to lock inode, but that is already held by task A - task A is interrupted, it tries to lock pipe->inode, but fails, as it is already held by task B - ABBA deadlock Fix this by explicitly ordering locks: the outer lock must be on target inode and the inner lock (which is later unlocked and relocked) must be on pipe->inode. This is OK, pipe inodes and target inodes form two nonoverlapping sets, generic_file_splice_write() and friends are not called with a target which is a pipe. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Acked-by: Mark Fasheh <mfasheh@suse.com> Acked-by: Jens Axboe <jens.axboe@oracle.com> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/ocfs2')
-rw-r--r--fs/ocfs2/file.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index a5887df2cd8..8672b953603 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1926,7 +1926,7 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
out->f_path.dentry->d_name.len,
out->f_path.dentry->d_name.name);
- inode_double_lock(inode, pipe->inode);
+ mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
ret = ocfs2_rw_lock(inode, 1);
if (ret < 0) {
@@ -1941,12 +1941,16 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
goto out_unlock;
}
+ if (pipe->inode)
+ mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_CHILD);
ret = generic_file_splice_write_nolock(pipe, out, ppos, len, flags);
+ if (pipe->inode)
+ mutex_unlock(&pipe->inode->i_mutex);
out_unlock:
ocfs2_rw_unlock(inode, 1);
out:
- inode_double_unlock(inode, pipe->inode);
+ mutex_unlock(&inode->i_mutex);
mlog_exit(ret);
return ret;