dentry_lookup() combines locking the directory and performing a lookup
prior to a change to the directory.
Abstracting this prepares for changing the locking requirements.
dentry_lookup_noperm() does the same without needing a mnt_idmap and
without checking permissions. This is useful for internal filesystem
management (e.g. creating virtual files in response to events) and in
other cases similar to lookup_noperm().
dentry_lookup_hashed() also does no permissions checking and assumes
that the hash of the name has already been stored in the qstr. This is
useful following filename_parentat().
These are intended to be paired with done_dentry_lookup() which provides
the inverse of putting the dentry and unlocking.
Like lookup_one_qstr_excl(), dentry_lookup() returns -ENOENT if
LOOKUP_CREATE was NOT given and the name cannot be found,, and returns
-EEXIST if LOOKUP_EXCL WAS given and the name CAN be found.
These functions replace all uses of lookup_one_qstr_excl() in namei.c
except for those used for rename.
Some of the variants should possibly be inlines in a header.
Signed-off-by: NeilBrown <neil@xxxxxxxxxx>
---
fs/namei.c | 158 ++++++++++++++++++++++++++++++------------
include/linux/namei.h | 8 ++-
2 files changed, 119 insertions(+), 47 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 950a0d0d54da..f292df61565a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1714,17 +1714,98 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name,
}
EXPORT_SYMBOL(lookup_one_qstr_excl);
+/**
+ * dentry_lookup_hashed - lookup and lock a name prior to dir ops
+ * @last: the name in the given directory
+ * @base: the directory in which the name is to be found
+ * @lookup_flags: %LOOKUP_xxx flags
+ *
+ * The name is looked up and necessary locks are taken so that
+ * the name can be created or removed.
+ * The "necessary locks" are currently the inode node lock on @base.
+ * The name @last is expected to already have the hash calculated.
+ * No permission checks are performed.
+ * Returns: the dentry, suitably locked, or an ERR_PTR().
+ */
+struct dentry *dentry_lookup_hashed(struct qstr *last,
+ struct dentry *base,
+ unsigned int lookup_flags)
+{
+ struct dentry *dentry;
+
+ inode_lock_nested(base->d_inode, I_MUTEX_PARENT);
+
+ dentry = lookup_one_qstr_excl(last, base, lookup_flags);
+ if (IS_ERR(dentry))
+ inode_unlock(base->d_inode);
+ return dentry;
+}
+EXPORT_SYMBOL(dentry_lookup_hashed);
+
+static int lookup_noperm_common(struct qstr *qname, struct dentry *base);
+static int lookup_one_common(struct mnt_idmap *idmap,
+ struct qstr *qname, struct dentry *base);
+
+/**
+ * dentry_lookup_noperm - lookup and lock a name prior to dir ops
+ * @last: the name in the given directory
+ * @base: the directory in which the name is to be found
+ * @lookup_flags: %LOOKUP_xxx flags
+ *
+ * The name is looked up and necessary locks are taken so that
+ * the name can be created or removed.
+ * The "necessary locks" are currently the inode node lock on @base.
+ * The name @last is NOT expected to have the hash calculated.
+ * No permission checks are performed.
+ * Returns: the dentry, suitably locked, or an ERR_PTR().
+ */
+struct dentry *dentry_lookup_noperm(struct qstr *last,
+ struct dentry *base,
+ unsigned int lookup_flags)
+{
+ int err;
+
+ err = lookup_noperm_common(last, base);
+ if (err < 0)
+ return ERR_PTR(err);
+ return dentry_lookup_hashed(last, base, lookup_flags);
+}
+EXPORT_SYMBOL(dentry_lookup_noperm);
+
+/**
+ * dentry_lookup - lookup and lock a name prior to dir ops
+ * @last: the name in the given directory
+ * @base: the directory in which the name is to be found
+ * @lookup_flags: %LOOKUP_xxx flags
+ *
+ * The name is looked up and necessary locks are taken so that
+ * the name can be created or removed.
+ * The "necessary locks" are currently the inode node lock on @base.
+ * The name @last is NOT expected to already have the hash calculated.
+ * Permission checks are performed to ensure %MAY_EXEC access to @base.
+ * Returns: the dentry, suitably locked, or an ERR_PTR().
+ */
+struct dentry *dentry_lookup(struct mnt_idmap *idmap,
+ struct qstr *last,
+ struct dentry *base,
+ unsigned int lookup_flags)
+{
+ int err;
+
+ err = lookup_one_common(idmap, last, base);
+ if (err < 0)
+ return ERR_PTR(err);
+ return dentry_lookup_hashed(last, base, lookup_flags);
+}
+EXPORT_SYMBOL(dentry_lookup);
+
/**
* done_dentry_lookup - finish a lookup used for create/delete
* @dentry: the target dentry
*
- * After locking the directory and lookup or validating a dentry
- * an attempt can be made to create (including link) or remove (including
- * rmdir) a dentry. After this, done_dentry_lookup() can be used to both
- * unlock the parent directory and dput() the dentry.
- *
- * If the dentry is an error - as can happen after vfs_mkdir() -
- * the unlock is skipped as unneeded.
+ * Reverse the effects of dentry_lookup() or similar. If the
+ * @dentry is not an error, the lock and the reference to the dentry
+ * are dropped.
*
* This interface allows a smooth transition from parent-dir based
* locking to dentry based locking.
@@ -1733,6 +1814,7 @@ void done_dentry_lookup(struct dentry *dentry)
{
if (!IS_ERR(dentry)) {
inode_unlock(dentry->d_parent->d_inode);
+ d_lookup_done(dentry);
dput(dentry);
}
}
@@ -1742,16 +1824,16 @@ EXPORT_SYMBOL(done_dentry_lookup);
* done_dentry_lookup_return - finish a lookup sequence, returning the dentry
* @dentry: the target dentry
*
- * After locking the directory and lookup or validating a dentry
- * an attempt can be made to create (including link) or remove (including
- * rmdir) a dentry. After this, done_dentry_lookup_return() can be used to
- * unlock the parent directory. The dentry is returned for further use.
+ * Reverse the effects of dentry_lookup() or similar, but keep the dentry.
+ * If @dentry is not an error, the lock is dropped.
*
* If the dentry is an error - as can happen after vfs_mkdir() -
* the unlock is skipped as unneeded.
*
* This interface allows a smooth transition from parent-dir based
* locking to dentry based locking.
+ *
+ * Returns: the dentry.
*/
struct dentry *done_dentry_lookup_return(struct dentry *dentry)
{
@@ -2803,12 +2885,9 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct
return ERR_PTR(error);
if (unlikely(type != LAST_NORM))
return ERR_PTR(-EINVAL);
- inode_lock_nested(parent_path.dentry->d_inode, I_MUTEX_PARENT);
- d = lookup_one_qstr_excl(&last, parent_path.dentry, 0);
- if (IS_ERR(d)) {
- inode_unlock(parent_path.dentry->d_inode);
+ d = dentry_lookup_hashed(&last, parent_path.dentry, 0);
+ if (IS_ERR(d))
return d;
- }
path->dentry = no_free_ptr(parent_path.dentry);
path->mnt = no_free_ptr(parent_path.mnt);
return d;
@@ -2827,12 +2906,9 @@ struct dentry *kern_path_locked_negative(const char *name, struct path *path)
return ERR_PTR(error);
if (unlikely(type != LAST_NORM))
return ERR_PTR(-EINVAL);
- inode_lock_nested(parent_path.dentry->d_inode, I_MUTEX_PARENT);
- d = lookup_one_qstr_excl(&last, parent_path.dentry, LOOKUP_CREATE);
- if (IS_ERR(d)) {
- inode_unlock(parent_path.dentry->d_inode);
+ d = dentry_lookup_hashed(&last, parent_path.dentry, LOOKUP_CREATE);
+ if (IS_ERR(d))
return d;
- }
path->dentry = no_free_ptr(parent_path.dentry);
path->mnt = no_free_ptr(parent_path.mnt);
return d;
@@ -4161,7 +4237,6 @@ static struct dentry *filename_create(int dfd, struct filename *name,
unsigned int reval_flag = lookup_flags & LOOKUP_REVAL;
unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL;
int type;
- int err2;
int error;
error = filename_parentat(dfd, name, reval_flag, path, &last, &type);
@@ -4173,35 +4248,30 @@ static struct dentry *filename_create(int dfd, struct filename *name,
* (foo/., foo/.., /////)
*/
if (unlikely(type != LAST_NORM))
- goto out;
+ goto put;
/* don't fail immediately if it's r/o, at least try to report other errors */
- err2 = mnt_want_write(path->mnt);
+ error = mnt_want_write(path->mnt);
/*
* Do the final lookup. Suppress 'create' if there is a trailing
* '/', and a directory wasn't requested.
*/
if (last.name[last.len] && !want_dir)
create_flags &= ~LOOKUP_CREATE;
- inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
- dentry = lookup_one_qstr_excl(&last, path->dentry,
- reval_flag | create_flags);
+ dentry = dentry_lookup_hashed(&last, path->dentry, reval_flag | create_flags);
if (IS_ERR(dentry))
- goto unlock;
+ goto drop;
- if (unlikely(err2)) {
- error = err2;
+ if (unlikely(error))
goto fail;
- }
return dentry;
fail:
- dput(dentry);
+ done_dentry_lookup(dentry);
dentry = ERR_PTR(error);
-unlock:
- inode_unlock(path->dentry->d_inode);
- if (!err2)
+drop:
+ if (!error)
mnt_drop_write(path->mnt);
-out:
+put:
path_put(path);
return dentry;
}
@@ -4225,7 +4295,7 @@ void done_path_create(struct path *path, struct dentry *dentry)
}
EXPORT_SYMBOL(done_path_create);
-inline struct dentry *user_path_create(int dfd, const char __user *pathname,
+struct dentry *user_path_create(int dfd, const char __user *pathname,
struct path *path, unsigned int lookup_flags)
{
struct filename *filename = getname(pathname);
@@ -4551,19 +4621,18 @@ int do_rmdir(int dfd, struct filename *name)
if (error)
goto exit2;
- inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
- dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
+ dentry = dentry_lookup_hashed(&last, path.dentry, lookup_flags);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto exit3;
+
error = security_path_rmdir(&path, dentry);
if (error)
goto exit4;
error = vfs_rmdir(mnt_idmap(path.mnt), path.dentry->d_inode, dentry);
exit4:
- dput(dentry);
+ done_dentry_lookup(dentry);
exit3:
- inode_unlock(path.dentry->d_inode);
mnt_drop_write(path.mnt);
exit2:
path_put(&path);
@@ -4680,11 +4749,9 @@ int do_unlinkat(int dfd, struct filename *name)
if (error)
goto exit2;
retry_deleg:
- inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
- dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
+ dentry = dentry_lookup_hashed(&last, path.dentry, lookup_flags);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
-
/* Why not before? Because we want correct error value */
if (last.name[last.len])
goto slashes;
@@ -4696,9 +4763,8 @@ int do_unlinkat(int dfd, struct filename *name)
error = vfs_unlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, &delegated_inode);
exit3:
- dput(dentry);
+ done_dentry_lookup(dentry);
}
- inode_unlock(path.dentry->d_inode);
if (inode)
iput(inode); /* truncate the inode here */
inode = NULL;
diff --git a/include/linux/namei.h b/include/linux/namei.h
index e097f11587c9..6d2cf4af5f16 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -80,7 +80,13 @@ struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
struct qstr *name,
struct dentry *base);
-
+struct dentry *dentry_lookup(struct mnt_idmap *idmap,
+ struct qstr *last, struct dentry *base,
+ unsigned int lookup_flags);
+struct dentry *dentry_lookup_noperm(struct qstr *name, struct dentry *base,
+ unsigned int lookup_flags);
+struct dentry *dentry_lookup_hashed(struct qstr *last, struct dentry *base,
+ unsigned int lookup_flags);
void done_dentry_lookup(struct dentry *dentry);
struct dentry *done_dentry_lookup_return(struct dentry *dentry);
--
2.49.0
