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| author | Miklos Szeredi <miklos@szeredi.hu> | 2006-02-04 23:27:40 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-02-05 11:06:51 -0800 |
| commit | 7128ec2a747d7a5f3c764c37bef17081ccc2374c (patch) | |
| tree | 10781a63d46811789e1cd26964f1d0a9eb963ce2 /fs | |
| parent | e22bec266cd6f540da2a61db216914c3473135cc (diff) | |
| download | linux-7128ec2a747d7a5f3c764c37bef17081ccc2374c.tar.gz | |
[PATCH] fuse: fix request_end() vs fuse_reset_request() race
The last fix for this function in fact opened up a much more often triggering race. It was uncommented tricky code, that was buggy. Add comment, make it less tricky and fix bug. Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/fuse/dev.c | 40 |
1 files changed, 29 insertions, 11 deletions
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 4526da8907c6..f556a0d5c0d3 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -120,9 +120,9 @@ struct fuse_req *fuse_get_request(struct fuse_conn *fc) return do_get_request(fc); } +/* Must be called with fuse_lock held */ static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req) { - spin_lock(&fuse_lock); if (req->preallocated) { atomic_dec(&fc->num_waiting); list_add(&req->list, &fc->unused_list); @@ -134,11 +134,19 @@ static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req) fc->outstanding_debt--; else up(&fc->outstanding_sem); - spin_unlock(&fuse_lock); } void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req) { + if (atomic_dec_and_test(&req->count)) { + spin_lock(&fuse_lock); + fuse_putback_request(fc, req); + spin_unlock(&fuse_lock); + } +} + +static void fuse_put_request_locked(struct fuse_conn *fc, struct fuse_req *req) +{ if (atomic_dec_and_test(&req->count)) fuse_putback_request(fc, req); } @@ -163,26 +171,36 @@ void fuse_release_background(struct fuse_req *req) * still waiting), the 'end' callback is called if given, else the * reference to the request is released * + * Releasing extra reference for foreground requests must be done + * within the same locked region as setting state to finished. This + * is because fuse_reset_request() may be called after request is + * finished and it must be the sole possessor. If request is + * interrupted and put in the background, it will return with an error + * and hence never be reset and reused. + * * Called with fuse_lock, unlocks it */ static void request_end(struct fuse_conn *fc, struct fuse_req *req) { - void (*end) (struct fuse_conn *, struct fuse_req *) = req->end; - req->end = NULL; list_del(&req->list); req->state = FUSE_REQ_FINISHED; - spin_unlock(&fuse_lock); - if (req->background) { + if (!req->background) { + wake_up(&req->waitq); + fuse_put_request_locked(fc, req); + spin_unlock(&fuse_lock); + } else { + void (*end) (struct fuse_conn *, struct fuse_req *) = req->end; + req->end = NULL; + spin_unlock(&fuse_lock); down_read(&fc->sbput_sem); if (fc->mounted) fuse_release_background(req); up_read(&fc->sbput_sem); + if (end) + end(fc, req); + else + fuse_put_request(fc, req); } - wake_up(&req->waitq); - if (end) - end(fc, req); - else - fuse_put_request(fc, req); } /* |