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[PATCH] Take i_mutex in splice_from_pipe()

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The splice_actor may be calling ->prepare_write() and ->commit_write(). We
want i_mutex on the inode being written to before calling those so that we
don't race i_size changes.

The double locking behavior is done elsewhere in splice.c, and if we
eventually want _nolock variants of generic_file_splice_write(), fs modules
might have to replicate the nasty locking code. We introduce
inode_double_lock() and inode_double_unlock() to consolidate the locking
rules into one set of functions.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Mark Fasheh
2006-10-17 10:31:38 +02:00
committed by Jens Axboe
parent ce9e3d9953
commit 62752ee198
3 changed files with 50 additions and 13 deletions
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24
fs/splice.c
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@@ -713,6 +713,7 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
{
int ret, do_wakeup, err;
struct splice_desc sd;
struct inode *inode = out->f_mapping->host;
ret = 0;
do_wakeup = 0;
@@ -722,8 +723,13 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
sd.file = out;
sd.pos = *ppos;
if (pipe->inode)
mutex_lock(&pipe->inode->i_mutex);
/*
* The actor worker might be calling ->prepare_write and
* ->commit_write. Most of the time, these expect i_mutex to
* be held. Since this may result in an ABBA deadlock with
* pipe->inode, we have to order lock acquiry here.
*/
inode_double_lock(inode, pipe->inode);
for (;;) {
if (pipe->nrbufs) {
@@ -797,8 +803,7 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
pipe_wait(pipe);
}
if (pipe->inode)
mutex_unlock(&pipe->inode->i_mutex);
inode_double_unlock(inode, pipe->inode);
if (do_wakeup) {
smp_mb();
@@ -1400,13 +1405,7 @@ static int link_pipe(struct pipe_inode_info *ipipe,
* grabbing by inode address. Otherwise two different processes
* could deadlock (one doing tee from A -> B, the other from B -> A).
*/
if (ipipe->inode < opipe->inode) {
mutex_lock_nested(&ipipe->inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&opipe->inode->i_mutex, I_MUTEX_CHILD);
} else {
mutex_lock_nested(&opipe->inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&ipipe->inode->i_mutex, I_MUTEX_CHILD);
}
inode_double_lock(ipipe->inode, opipe->inode);
do {
if (!opipe->readers) {
@@ -1450,8 +1449,7 @@ static int link_pipe(struct pipe_inode_info *ipipe,
i++;
} while (len);
mutex_unlock(&ipipe->inode->i_mutex);
mutex_unlock(&opipe->inode->i_mutex);
inode_double_unlock(ipipe->inode, opipe->inode);
/*
* If we put data in the output pipe, wakeup any potential readers.