From 73ce8355c243a434524a34c05cc417dd0467996e Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Tue, 11 Apr 2006 21:14:26 +0200 Subject: [fuse] fix deadlock between fuse_put_super() and request_end() 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 chosen soltuion is to get rid of sbput_sem, and instead use the spinlock to ensure the referenced inodes/file are released only once. Since the actual release may sleep, defer these outside the locked region, but using local variables instead of the structure members. This is a much more rubust solution. Signed-off-by: Miklos Szeredi --- fs/fuse/dev.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) (limited to 'fs/fuse/dev.c') diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 6c740f86066..d4efb6223e2 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -120,20 +120,14 @@ void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req) } } -void fuse_release_background(struct fuse_conn *fc, struct fuse_req *req) +void fuse_remove_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); + list_del_init(&req->bg_entry); if (fc->num_background == FUSE_MAX_BACKGROUND) { fc->blocked = 0; wake_up_all(&fc->blocked_waitq); } fc->num_background--; - spin_unlock(&fc->lock); } /* @@ -163,17 +157,27 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req) wake_up(&req->waitq); fuse_put_request(fc, req); } else { + struct inode *inode = req->inode; + struct inode *inode2 = req->inode2; + struct file *file = req->file; void (*end) (struct fuse_conn *, struct fuse_req *) = req->end; req->end = NULL; + req->inode = NULL; + req->inode2 = NULL; + req->file = NULL; + if (!list_empty(&req->bg_entry)) + fuse_remove_background(fc, req); spin_unlock(&fc->lock); - down_read(&fc->sbput_sem); - if (fc->mounted) - fuse_release_background(fc, req); - up_read(&fc->sbput_sem); + if (end) end(fc, req); else fuse_put_request(fc, req); + + if (file) + fput(file); + iput(inode); + iput(inode2); } } -- cgit v1.2.3