diff options
| -rw-r--r-- | fs/fuse/dir.c | 99 |
1 files changed, 90 insertions, 9 deletions
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 4c127f2bc814..fead7f49e2ca 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -14,6 +14,15 @@ #include <linux/sched.h> #include <linux/namei.h> +/* + * FUSE caches dentries and attributes with separate timeout. The + * time in jiffies until the dentry/attributes are valid is stored in + * dentry->d_time and fuse_inode->i_time respectively. + */ + +/* + * Calculate the time in jiffies until a dentry/attributes are valid + */ static inline unsigned long time_to_jiffies(unsigned long sec, unsigned long nsec) { @@ -21,6 +30,10 @@ static inline unsigned long time_to_jiffies(unsigned long sec, return jiffies + timespec_to_jiffies(&ts); } +/* + * Set dentry and possibly attribute timeouts from the lookup/mk* + * replies + */ static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o) { entry->d_time = time_to_jiffies(o->entry_valid, o->entry_valid_nsec); @@ -29,16 +42,32 @@ static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o) time_to_jiffies(o->attr_valid, o->attr_valid_nsec); } +/* + * Mark the attributes as stale, so that at the next call to + * ->getattr() they will be fetched from userspace + */ void fuse_invalidate_attr(struct inode *inode) { get_fuse_inode(inode)->i_time = jiffies - 1; } +/* + * Just mark the entry as stale, so that a next attempt to look it up + * will result in a new lookup call to userspace + * + * This is called when a dentry is about to become negative and the + * timeout is unknown (unlink, rmdir, rename and in some cases + * lookup) + */ static void fuse_invalidate_entry_cache(struct dentry *entry) { entry->d_time = jiffies - 1; } +/* + * Same as fuse_invalidate_entry_cache(), but also try to remove the + * dentry from the hash + */ static void fuse_invalidate_entry(struct dentry *entry) { d_invalidate(entry); @@ -60,6 +89,15 @@ static void fuse_lookup_init(struct fuse_req *req, struct inode *dir, req->out.args[0].value = outarg; } +/* + * Check whether the dentry is still valid + * + * If the entry validity timeout has expired and the dentry is + * positive, try to redo the lookup. If the lookup results in a + * different inode, then let the VFS invalidate the dentry and redo + * the lookup once more. If the lookup results in the same inode, + * then refresh the attributes, timeouts and mark the dentry valid. + */ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd) { struct inode *inode = entry->d_inode; @@ -72,6 +110,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd) struct fuse_conn *fc; struct fuse_req *req; + /* Doesn't hurt to "reset" the validity timeout */ fuse_invalidate_entry_cache(entry); if (!inode) return 0; @@ -102,10 +141,13 @@ 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)) { - /* Don't allow creating an alias to a directory */ struct dentry *alias = d_find_alias(inode); if (alias) { dput(alias); @@ -170,6 +212,12 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry, return NULL; } +/* + * Atomic create+open operation + * + * If the filesystem doesn't support this, then fall back to separate + * 'mknod' + 'open' requests. + */ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode, struct nameidata *nd) { @@ -236,6 +284,9 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode, if (!inode) { flags &= ~(O_CREAT | O_EXCL | O_TRUNC); ff->fh = outopen.fh; + /* Special release, with inode = NULL, this will + trigger a 'forget' request when the release is + complete */ fuse_send_release(fc, ff, outentry.nodeid, NULL, flags, 0); goto out_put_request; } @@ -259,6 +310,9 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode, return err; } +/* + * Code shared between mknod, mkdir, symlink and link + */ static int create_new_entry(struct fuse_conn *fc, struct fuse_req *req, struct inode *dir, struct dentry *entry, int mode) @@ -576,6 +630,15 @@ static int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task) return 0; } +/* + * Check whether the inode attributes are still valid + * + * If the attribute validity timeout has expired, then fetch the fresh + * attributes with a 'getattr' request + * + * I'm not sure why cached attributes are never returned for the root + * inode, this is probably being too cautious. + */ static int fuse_revalidate(struct dentry *entry) { struct inode *inode = entry->d_inode; @@ -623,6 +686,19 @@ static int fuse_access(struct inode *inode, int mask) return err; } +/* + * Check permission. The two basic access models of FUSE are: + * + * 1) Local access checking ('default_permissions' mount option) based + * on file mode. This is the plain old disk filesystem permission + * modell. + * + * 2) "Remote" access checking, where server is responsible for + * checking permission in each inode operation. An exception to this + * is if ->permission() was invoked from sys_access() in which case an + * access request is sent. Execute permission is still checked + * locally based on file mode. + */ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd) { struct fuse_conn *fc = get_fuse_conn(inode); @@ -641,14 +717,10 @@ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd) err = generic_permission(inode, mask, NULL); } - /* FIXME: Need some mechanism to revoke permissions: - currently if the filesystem suddenly changes the - file mode, we will not be informed about it, and - continue to allow access to the file/directory. - - This is actually not so grave, since the user can - simply keep access to the file/directory anyway by - keeping it open... */ + /* Note: the opposite of the above test does not + exist. So if permissions are revoked this won't be + noticed immediately, only after the attribute + timeout has expired */ return err; } else { @@ -816,6 +888,15 @@ static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg) } } +/* + * Set attributes, and at the same time refresh them. + * + * Truncation is slightly complicated, because the 'truncate' request + * may fail, in which case we don't want to touch the mapping. + * vmtruncate() doesn't allow for this case. So do the rlimit + * checking by hand and call vmtruncate() only after the file has + * actually been truncated. + */ static int fuse_setattr(struct dentry *entry, struct iattr *attr) { struct inode *inode = entry->d_inode; |