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Subject[PATCH v3 088/110] namei: path_init() calling conventions change
Date
From: Al Viro <viro@zeniv.linux.org.uk>

* lift link_path_walk() into callers; moving it down into path_init()
had been a mistake. Stack footprint, among other things...
* do _not_ call path_cleanup() after path_init() failure; on all failure
exits out of it we have nothing for path_cleanup() to do
* have path_init() return pathname or ERR_PTR(-E...)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namei.c | 69 +++++++++++++++++++++++++++++++-------------------------------
1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 497d5f4..06c7120 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1821,11 +1821,11 @@ static int link_path_walk(const char *name, struct nameidata *nd)
} while (unlikely(*name == '/'));
if (unlikely(!*name)) {
OK:
- /* called from path_init(), done */
+ /* pathname body, done */
if (!nd->depth)
return 0;
name = nd->stack[nd->depth - 1].name;
- /* called from trailing_symlink(), done */
+ /* trailing symlink, done */
if (!name)
return 0;
/* last component of nested symlink */
@@ -1862,8 +1862,8 @@ OK:
return err;
}

-static int path_init(int dfd, const struct filename *name, unsigned int flags,
- struct nameidata *nd)
+static const char *path_init(int dfd, const struct filename *name,
+ unsigned int flags, struct nameidata *nd)
{
int retval = 0;
const char *s = name->name;
@@ -1871,15 +1871,16 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
nd->depth = 0;
+ nd->total_link_count = 0;
if (flags & LOOKUP_ROOT) {
struct dentry *root = nd->root.dentry;
struct inode *inode = root->d_inode;
if (*s) {
if (!d_can_lookup(root))
- return -ENOTDIR;
+ return ERR_PTR(-ENOTDIR);
retval = inode_permission(inode, MAY_EXEC);
if (retval)
- return retval;
+ return ERR_PTR(retval);
}
nd->path = nd->root;
nd->inode = inode;
@@ -1890,7 +1891,7 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
} else {
path_get(&nd->path);
}
- goto done;
+ return s;
}

nd->root.mnt = NULL;
@@ -1926,14 +1927,14 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
struct dentry *dentry;

if (!f.file)
- return -EBADF;
+ return ERR_PTR(-EBADF);

dentry = f.file->f_path.dentry;

if (*s) {
if (!d_can_lookup(dentry)) {
fdput(f);
- return -ENOTDIR;
+ return ERR_PTR(-ENOTDIR);
}
}

@@ -1947,21 +1948,18 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
nd->inode = nd->path.dentry->d_inode;
}
fdput(f);
- goto done;
+ return s;
}

nd->inode = nd->path.dentry->d_inode;
if (!(flags & LOOKUP_RCU))
- goto done;
+ return s;
if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
- goto done;
+ return s;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
- return -ECHILD;
-done:
- nd->total_link_count = 0;
- return link_path_walk(s, nd);
+ return ERR_PTR(-ECHILD);
}

static void path_cleanup(struct nameidata *nd)
@@ -2014,23 +2012,12 @@ static inline int lookup_last(struct nameidata *nd)
static int path_lookupat(int dfd, const struct filename *name,
unsigned int flags, struct nameidata *nd)
{
+ const char *s = path_init(dfd, name, flags, nd);
int err;

- /*
- * Path walking is largely split up into 2 different synchronisation
- * schemes, rcu-walk and ref-walk (explained in
- * Documentation/filesystems/path-lookup.txt). These share much of the
- * path walk code, but some things particularly setup, cleanup, and
- * following mounts are sufficiently divergent that functions are
- * duplicated. Typically there is a function foo(), and its RCU
- * analogue, foo_rcu().
- *
- * -ECHILD is the error number of choice (just to avoid clashes) that
- * is returned if some aspect of an rcu-walk fails. Such an error must
- * be handled by restarting a traditional ref-walk (which will always
- * be able to complete).
- */
- err = path_init(dfd, name, flags, nd);
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+ err = link_path_walk(s, nd);
if (!err) {
while ((err = lookup_last(nd)) > 0) {
err = trailing_symlink(nd);
@@ -2075,7 +2062,11 @@ static int filename_lookup(int dfd, struct filename *name,
static int path_parentat(int dfd, const struct filename *name,
unsigned int flags, struct nameidata *nd)
{
- int err = path_init(dfd, name, flags | LOOKUP_PARENT, nd);
+ const char *s = path_init(dfd, name, flags, nd);
+ int err;
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+ err = link_path_walk(s, nd);
if (!err)
err = complete_walk(nd);
path_cleanup(nd);
@@ -2406,7 +2397,11 @@ static int
path_mountpoint(int dfd, const struct filename *name, struct path *path,
struct nameidata *nd, unsigned int flags)
{
- int err = path_init(dfd, name, flags, nd);
+ const char *s = path_init(dfd, name, flags, nd);
+ int err;
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+ err = link_path_walk(s, nd);
if (unlikely(err))
goto out;

@@ -3266,6 +3261,7 @@ out:
static struct file *path_openat(int dfd, struct filename *pathname,
struct nameidata *nd, const struct open_flags *op, int flags)
{
+ const char *s;
struct file *file;
int opened = 0;
int error;
@@ -3281,7 +3277,12 @@ static struct file *path_openat(int dfd, struct filename *pathname,
goto out2;
}

- error = path_init(dfd, pathname, flags, nd);
+ s = path_init(dfd, pathname, flags, nd);
+ if (IS_ERR(s)) {
+ put_filp(file);
+ return ERR_CAST(s);
+ }
+ error = link_path_walk(s, nd);
if (unlikely(error))
goto out;

--
2.1.4


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