From 33649c91a3df57c1090a657637d44b896de367e7 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Sun, 25 Jun 2006 05:48:52 -0700 Subject: [PATCH] fuse: ensure FLUSH reaches userspace All POSIX locks owned by the current task are removed on close(). If the FLUSH request resulting initiated by close() fails to reach userspace, there might be locks remaining, which cannot be removed. The only reason it could fail, is if allocating the request fails. In this case use the request reserved for RELEASE, or if that is currently used by another FLUSH, wait for it to become available. Signed-off-by: Miklos Szeredi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fuse/dev.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 84 insertions(+), 4 deletions(-) (limited to 'fs/fuse/dev.c') diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index fe3adf58917..ae26f37e53a 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -76,6 +76,13 @@ static void __fuse_put_request(struct fuse_req *req) atomic_dec(&req->count); } +static void fuse_req_init_context(struct fuse_req *req) +{ + req->in.h.uid = current->fsuid; + req->in.h.gid = current->fsgid; + req->in.h.pid = current->pid; +} + struct fuse_req *fuse_get_req(struct fuse_conn *fc) { struct fuse_req *req; @@ -100,9 +107,7 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc) if (!req) goto out; - req->in.h.uid = current->fsuid; - req->in.h.gid = current->fsgid; - req->in.h.pid = current->pid; + fuse_req_init_context(req); req->waiting = 1; return req; @@ -111,12 +116,87 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc) return ERR_PTR(err); } +/* + * Return request in fuse_file->reserved_req. However that may + * currently be in use. If that is the case, wait for it to become + * available. + */ +static struct fuse_req *get_reserved_req(struct fuse_conn *fc, + struct file *file) +{ + struct fuse_req *req = NULL; + struct fuse_file *ff = file->private_data; + + do { + wait_event(fc->blocked_waitq, ff->reserved_req); + spin_lock(&fc->lock); + if (ff->reserved_req) { + req = ff->reserved_req; + ff->reserved_req = NULL; + get_file(file); + req->stolen_file = file; + } + spin_unlock(&fc->lock); + } while (!req); + + return req; +} + +/* + * Put stolen request back into fuse_file->reserved_req + */ +static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req) +{ + struct file *file = req->stolen_file; + struct fuse_file *ff = file->private_data; + + spin_lock(&fc->lock); + fuse_request_init(req); + BUG_ON(ff->reserved_req); + ff->reserved_req = req; + wake_up(&fc->blocked_waitq); + spin_unlock(&fc->lock); + fput(file); +} + +/* + * Gets a requests for a file operation, always succeeds + * + * This is used for sending the FLUSH request, which must get to + * userspace, due to POSIX locks which may need to be unlocked. + * + * If allocation fails due to OOM, use the reserved request in + * fuse_file. + * + * This is very unlikely to deadlock accidentally, since the + * filesystem should not have it's own file open. If deadlock is + * intentional, it can still be broken by "aborting" the filesystem. + */ +struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file) +{ + struct fuse_req *req; + + atomic_inc(&fc->num_waiting); + wait_event(fc->blocked_waitq, !fc->blocked); + req = fuse_request_alloc(); + if (!req) + req = get_reserved_req(fc, file); + + fuse_req_init_context(req); + req->waiting = 1; + return req; +} + void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req) { if (atomic_dec_and_test(&req->count)) { if (req->waiting) atomic_dec(&fc->num_waiting); - fuse_request_free(req); + + if (req->stolen_file) + put_reserved_req(fc, req); + else + fuse_request_free(req); } } -- cgit v1.2.3