Commit 6f9f1180 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Linus Torvalds
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[PATCH] fuse: add code documentation



Document some not-so-trivial functions.
Signed-off-by: default avatarMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 8cbdf1e6
......@@ -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;
......
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