From: Miklos Szeredi Date: Tue, 17 Oct 2006 07:10:11 +0000 (-0700) Subject: [PATCH] fuse: fix handling of moved directory X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d2a85164aaa8d514ef5efbf5d05746e85dd13ddd;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git [PATCH] fuse: fix handling of moved directory Fuse considered it an error (EIO) if lookup returned a directory inode, to which a dentry already refered. This is because directory aliases are not allowed. But in a network filesystem this could happen legitimately, if a directory is moved on a remote client. This patch attempts to relax the restriction by trying to first evict the offending alias from the cache. If this fails, it still returns an error (EBUSY). A rarer situation is if an mkdir races with an indenpendent lookup, which finds the newly created directory already moved. In this situation the mkdir should return success, but that would be incorrect, since the dentry cannot be instantiated, so return EBUSY. Previously checking for a directory alias and instantiation of the dentry weren't done atomically in lookup/mkdir, hence two such calls racing with each other could create aliased directories. To prevent this introduce a new per-connection mutex: fuse_conn->inst_mutex, which is taken for instantiations with a directory inode. Signed-off-by: Miklos Szeredi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 7ecfe95795cd..9d0ef5e18740 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -177,22 +177,6 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd) return 1; } -/* - * Check if there's already a hashed alias of this directory inode. - * If yes, then lookup and mkdir must not create a new alias. - */ -static int dir_alias(struct inode *inode) -{ - if (S_ISDIR(inode->i_mode)) { - struct dentry *alias = d_find_alias(inode); - if (alias) { - dput(alias); - return 1; - } - } - return 0; -} - static int invalid_nodeid(u64 nodeid) { return !nodeid || nodeid == FUSE_ROOT_ID; @@ -208,6 +192,24 @@ static int valid_mode(int m) S_ISBLK(m) || S_ISFIFO(m) || S_ISSOCK(m); } +/* + * Add a directory inode to a dentry, ensuring that no other dentry + * refers to this inode. Called with fc->inst_mutex. + */ +static int fuse_d_add_directory(struct dentry *entry, struct inode *inode) +{ + struct dentry *alias = d_find_alias(inode); + if (alias) { + /* This tries to shrink the subtree below alias */ + fuse_invalidate_entry(alias); + dput(alias); + if (!list_empty(&inode->i_dentry)) + return -EBUSY; + } + d_add(entry, inode); + return 0; +} + static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry, struct nameidata *nd) { @@ -243,11 +245,17 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry, if (err && err != -ENOENT) return ERR_PTR(err); - if (inode && dir_alias(inode)) { - iput(inode); - return ERR_PTR(-EIO); - } - d_add(entry, inode); + if (inode && S_ISDIR(inode->i_mode)) { + mutex_lock(&fc->inst_mutex); + err = fuse_d_add_directory(entry, inode); + mutex_unlock(&fc->inst_mutex); + if (err) { + iput(inode); + return ERR_PTR(err); + } + } else + d_add(entry, inode); + entry->d_op = &fuse_dentry_operations; if (!err) fuse_change_timeout(entry, &outarg); @@ -403,12 +411,22 @@ static int create_new_entry(struct fuse_conn *fc, struct fuse_req *req, } fuse_put_request(fc, req); - if (dir_alias(inode)) { - iput(inode); - return -EIO; - } + if (S_ISDIR(inode->i_mode)) { + struct dentry *alias; + mutex_lock(&fc->inst_mutex); + alias = d_find_alias(inode); + if (alias) { + /* New directory must have moved since mkdir */ + mutex_unlock(&fc->inst_mutex); + dput(alias); + iput(inode); + return -EBUSY; + } + d_instantiate(entry, inode); + mutex_unlock(&fc->inst_mutex); + } else + d_instantiate(entry, inode); - d_instantiate(entry, inode); fuse_change_timeout(entry, &outarg); fuse_invalidate_attr(dir); return 0; diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 69c7750d55b8..91edb8932d90 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -239,6 +239,9 @@ struct fuse_conn { /** Lock protecting accessess to members of this structure */ spinlock_t lock; + /** Mutex protecting against directory alias creation */ + struct mutex inst_mutex; + /** Refcount */ atomic_t count; diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 4ee8f72e6380..fc4203570370 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -379,6 +379,7 @@ static struct fuse_conn *new_conn(void) fc = kzalloc(sizeof(*fc), GFP_KERNEL); if (fc) { spin_lock_init(&fc->lock); + mutex_init(&fc->inst_mutex); atomic_set(&fc->count, 1); init_waitqueue_head(&fc->waitq); init_waitqueue_head(&fc->blocked_waitq); @@ -398,8 +399,10 @@ static struct fuse_conn *new_conn(void) void fuse_conn_put(struct fuse_conn *fc) { - if (atomic_dec_and_test(&fc->count)) + if (atomic_dec_and_test(&fc->count)) { + mutex_destroy(&fc->inst_mutex); kfree(fc); + } } struct fuse_conn *fuse_conn_get(struct fuse_conn *fc)