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[fuse] fix deadlock between fuse_put_super() and request_end(), try #2

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A deadlock was possible, when the last reference to the superblock was
held due to a background request containing a file reference.

Releasing the file would release the vfsmount which in turn would
release the superblock.  Since sbput_sem is held during the fput() and
fuse_put_super() tries to acquire this same semaphore, a deadlock
results.

The solution is to move the fput() outside the region protected by
sbput_sem.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
This commit is contained in:
Miklos Szeredi 2006-04-26 10:49:06 +02:00
parent 5a5fb1ea74
commit 6dbbcb1205
1 changed files with 11 additions and 2 deletions
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13
fs/fuse/dev.c
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@ -128,12 +128,16 @@ void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
}
}
/*
* Called with sbput_sem held for read (request_end) or write
* (fuse_put_super). By the time fuse_put_super() is finished, all
* inodes belonging to background requests must be released, so the
* iputs have to be done within the locked region.
*/
void fuse_release_background(struct fuse_conn *fc, struct fuse_req *req)
{
iput(req->inode);
iput(req->inode2);
if (req->file)
fput(req->file);
spin_lock(&fc->lock);
list_del(&req->bg_entry);
if (fc->num_background == FUSE_MAX_BACKGROUND) {
@ -178,6 +182,11 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
if (fc->mounted)
fuse_release_background(fc, req);
up_read(&fc->sbput_sem);
/* fput must go outside sbput_sem, otherwise it can deadlock */
if (req->file)
fput(req->file);
if (end)
end(fc, req);
else