Messages in this thread Patch in this message | | | Subject | [PATCH 2/4] [fuse] fix deadlock between fuse_put_super() and request_end() | From | Miklos Szeredi <> | Date | Tue, 25 Apr 2006 10:39:00 +0200 |
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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>
---
fs/fuse/dev.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-)
cdea55d00688ed9a494345b131521a2cae36d42a diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 4967bd4..104a62d 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -128,12 +128,16 @@ void fuse_put_request(struct fuse_conn * } } +/* + * 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 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 -- 1.2.4 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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