[PATCH] fuse: add code documentation
Document some not-so-trivial functions. Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Miklos Szeredi
Linus Torvalds
parent
8cbdf1e6f6
commit
6f9f11806a
1 changed files with 90 additions and 9 deletions
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@ -14,6 +14,15 @@
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#include <linux/sched.h>
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#include <linux/namei.h>
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/*
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* FUSE caches dentries and attributes with separate timeout. The
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* time in jiffies until the dentry/attributes are valid is stored in
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* dentry->d_time and fuse_inode->i_time respectively.
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*/
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/*
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* Calculate the time in jiffies until a dentry/attributes are valid
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*/
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static inline unsigned long time_to_jiffies(unsigned long sec,
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unsigned long nsec)
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{
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@ -21,6 +30,10 @@ static inline unsigned long time_to_jiffies(unsigned long sec,
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return jiffies + timespec_to_jiffies(&ts);
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}
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/*
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* Set dentry and possibly attribute timeouts from the lookup/mk*
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* replies
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*/
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static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o)
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{
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entry->d_time = time_to_jiffies(o->entry_valid, o->entry_valid_nsec);
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@ -29,16 +42,32 @@ static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o)
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time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
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}
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/*
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* Mark the attributes as stale, so that at the next call to
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* ->getattr() they will be fetched from userspace
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*/
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void fuse_invalidate_attr(struct inode *inode)
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{
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get_fuse_inode(inode)->i_time = jiffies - 1;
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}
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/*
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* Just mark the entry as stale, so that a next attempt to look it up
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* will result in a new lookup call to userspace
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*
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* This is called when a dentry is about to become negative and the
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* timeout is unknown (unlink, rmdir, rename and in some cases
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* lookup)
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*/
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static void fuse_invalidate_entry_cache(struct dentry *entry)
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{
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entry->d_time = jiffies - 1;
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}
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/*
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* Same as fuse_invalidate_entry_cache(), but also try to remove the
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* dentry from the hash
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*/
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static void fuse_invalidate_entry(struct dentry *entry)
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{
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d_invalidate(entry);
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@ -60,6 +89,15 @@ static void fuse_lookup_init(struct fuse_req *req, struct inode *dir,
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req->out.args[0].value = outarg;
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}
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/*
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* Check whether the dentry is still valid
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*
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* If the entry validity timeout has expired and the dentry is
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* positive, try to redo the lookup. If the lookup results in a
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* different inode, then let the VFS invalidate the dentry and redo
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* the lookup once more. If the lookup results in the same inode,
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* then refresh the attributes, timeouts and mark the dentry valid.
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*/
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static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
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{
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struct inode *inode = entry->d_inode;
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@ -72,6 +110,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
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struct fuse_conn *fc;
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struct fuse_req *req;
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/* Doesn't hurt to "reset" the validity timeout */
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fuse_invalidate_entry_cache(entry);
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if (!inode)
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return 0;
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@ -102,10 +141,13 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
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return 1;
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}
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/*
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* Check if there's already a hashed alias of this directory inode.
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* If yes, then lookup and mkdir must not create a new alias.
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*/
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static int dir_alias(struct inode *inode)
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{
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if (S_ISDIR(inode->i_mode)) {
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/* Don't allow creating an alias to a directory */
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struct dentry *alias = d_find_alias(inode);
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if (alias) {
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dput(alias);
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@ -170,6 +212,12 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
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return NULL;
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}
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/*
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* Atomic create+open operation
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*
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* If the filesystem doesn't support this, then fall back to separate
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* 'mknod' + 'open' requests.
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*/
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static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
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struct nameidata *nd)
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{
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@ -236,6 +284,9 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
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if (!inode) {
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flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
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ff->fh = outopen.fh;
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/* Special release, with inode = NULL, this will
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trigger a 'forget' request when the release is
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complete */
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fuse_send_release(fc, ff, outentry.nodeid, NULL, flags, 0);
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goto out_put_request;
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}
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@ -259,6 +310,9 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
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return err;
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}
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/*
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* Code shared between mknod, mkdir, symlink and link
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*/
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static int create_new_entry(struct fuse_conn *fc, struct fuse_req *req,
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struct inode *dir, struct dentry *entry,
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int mode)
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@ -576,6 +630,15 @@ static int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task)
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return 0;
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}
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/*
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* Check whether the inode attributes are still valid
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*
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* If the attribute validity timeout has expired, then fetch the fresh
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* attributes with a 'getattr' request
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*
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* I'm not sure why cached attributes are never returned for the root
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* inode, this is probably being too cautious.
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*/
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static int fuse_revalidate(struct dentry *entry)
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{
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struct inode *inode = entry->d_inode;
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@ -623,6 +686,19 @@ static int fuse_access(struct inode *inode, int mask)
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return err;
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}
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/*
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* Check permission. The two basic access models of FUSE are:
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*
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* 1) Local access checking ('default_permissions' mount option) based
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* on file mode. This is the plain old disk filesystem permission
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* modell.
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*
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* 2) "Remote" access checking, where server is responsible for
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* checking permission in each inode operation. An exception to this
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* is if ->permission() was invoked from sys_access() in which case an
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* access request is sent. Execute permission is still checked
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* locally based on file mode.
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*/
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static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
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{
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struct fuse_conn *fc = get_fuse_conn(inode);
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@ -641,14 +717,10 @@ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
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err = generic_permission(inode, mask, NULL);
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}
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/* FIXME: Need some mechanism to revoke permissions:
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currently if the filesystem suddenly changes the
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file mode, we will not be informed about it, and
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continue to allow access to the file/directory.
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This is actually not so grave, since the user can
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simply keep access to the file/directory anyway by
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keeping it open... */
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/* Note: the opposite of the above test does not
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exist. So if permissions are revoked this won't be
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noticed immediately, only after the attribute
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timeout has expired */
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return err;
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} else {
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@ -816,6 +888,15 @@ static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg)
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}
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}
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/*
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* Set attributes, and at the same time refresh them.
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*
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* Truncation is slightly complicated, because the 'truncate' request
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* may fail, in which case we don't want to touch the mapping.
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* vmtruncate() doesn't allow for this case. So do the rlimit
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* checking by hand and call vmtruncate() only after the file has
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* actually been truncated.
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*/
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static int fuse_setattr(struct dentry *entry, struct iattr *attr)
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{
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struct inode *inode = entry->d_inode;
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