From 6dbbcb120570d747b00783820ee02d1e1bcf63de Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 26 Apr 2006 10:49:06 +0200 Subject: [fuse] fix deadlock between fuse_put_super() and request_end(), try #2 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 --- fs/fuse/dev.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'fs/fuse') diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 4967bd40b953..104a62dadb94 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -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 -- cgit v1.2.3-58-ga151