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Groups > linux.kernel > #1638951

[PATCH 05/14] VFS: Provide empty name qstr

From David Howells <dhowells@redhat.com>
Newsgroups linux.kernel
Subject [PATCH 05/14] VFS: Provide empty name qstr
Date 2017-05-10 18:30 +0200
Message-ID <tFCEX-2YC-31@gated-at.bofh.it> (permalink)
References <tFCvf-2Uw-1@gated-at.bofh.it>
Organization Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903

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Provide an empty name (ie. "") qstr for general use.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/dcache.c            |    8 ++++++--
 fs/gfs2/dir.c          |    3 +--
 fs/namei.c             |    3 +--
 fs/nsfs.c              |    3 +--
 fs/pipe.c              |    3 +--
 include/linux/dcache.h |    5 +++++
 6 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 95d71eda8142..9a17ee020996 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -90,6 +90,11 @@ EXPORT_SYMBOL(rename_lock);
 
 static struct kmem_cache *dentry_cache __read_mostly;
 
+const struct qstr empty_name = QSTR_INIT("", 0);
+EXPORT_SYMBOL(empty_name);
+const struct qstr slash_name = QSTR_INIT("/", 1);
+EXPORT_SYMBOL(slash_name);
+
 /*
  * This is the single most critical data structure when it comes
  * to the dcache: the hashtable for lookups. Somebody should try
@@ -1580,8 +1585,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	 */
 	dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
 	if (unlikely(!name)) {
-		static const struct qstr anon = QSTR_INIT("/", 1);
-		name = &anon;
+		name = &slash_name;
 		dname = dentry->d_iname;
 	} else if (name->len > DNAME_INLINE_LEN-1) {
 		size_t size = offsetof(struct external_name, name[1]);
diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 79113219be5f..a5dfff6a033e 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -872,7 +872,6 @@ static struct gfs2_leaf *new_leaf(struct inode *inode, struct buffer_head **pbh,
 	struct buffer_head *bh;
 	struct gfs2_leaf *leaf;
 	struct gfs2_dirent *dent;
-	struct qstr name = { .name = "" };
 	struct timespec tv = current_time(inode);
 
 	error = gfs2_alloc_blocks(ip, &bn, &n, 0, NULL);
@@ -896,7 +895,7 @@ static struct gfs2_leaf *new_leaf(struct inode *inode, struct buffer_head **pbh,
 	leaf->lf_sec = cpu_to_be64(tv.tv_sec);
 	memset(leaf->lf_reserved2, 0, sizeof(leaf->lf_reserved2));
 	dent = (struct gfs2_dirent *)(leaf+1);
-	gfs2_qstr2dirent(&name, bh->b_size - sizeof(struct gfs2_leaf), dent);
+	gfs2_qstr2dirent(&empty_name, bh->b_size - sizeof(struct gfs2_leaf), dent);
 	*pbh = bh;
 	return leaf;
 }
diff --git a/fs/namei.c b/fs/namei.c
index 19dcf62133cc..0c2af2c7794f 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3368,7 +3368,6 @@ static int do_last(struct nameidata *nd,
 
 struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode, int open_flag)
 {
-	static const struct qstr name = QSTR_INIT("/", 1);
 	struct dentry *child = NULL;
 	struct inode *dir = dentry->d_inode;
 	struct inode *inode;
@@ -3382,7 +3381,7 @@ struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode, int open_flag)
 	if (!dir->i_op->tmpfile)
 		goto out_err;
 	error = -ENOMEM;
-	child = d_alloc(dentry, &name);
+	child = d_alloc(dentry, &slash_name);
 	if (unlikely(!child))
 		goto out_err;
 	error = dir->i_op->tmpfile(dir, child, mode);
diff --git a/fs/nsfs.c b/fs/nsfs.c
index 323f492e0822..253cf59b27a1 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -53,7 +53,6 @@ static void nsfs_evict(struct inode *inode)
 static void *__ns_get_path(struct path *path, struct ns_common *ns)
 {
 	struct vfsmount *mnt = nsfs_mnt;
-	struct qstr qname = { .name = "", };
 	struct dentry *dentry;
 	struct inode *inode;
 	unsigned long d;
@@ -85,7 +84,7 @@ static void *__ns_get_path(struct path *path, struct ns_common *ns)
 	inode->i_fop = &ns_file_operations;
 	inode->i_private = ns;
 
-	dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
+	dentry = d_alloc_pseudo(mnt->mnt_sb, &empty_name);
 	if (!dentry) {
 		iput(inode);
 		return ERR_PTR(-ENOMEM);
diff --git a/fs/pipe.c b/fs/pipe.c
index 73b84baf58f8..97e5be897753 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -739,13 +739,12 @@ int create_pipe_files(struct file **res, int flags)
 	struct inode *inode = get_pipe_inode();
 	struct file *f;
 	struct path path;
-	static struct qstr name = { .name = "" };
 
 	if (!inode)
 		return -ENFILE;
 
 	err = -ENOMEM;
-	path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
+	path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &empty_name);
 	if (!path.dentry)
 		goto err_inode;
 	path.mnt = mntget(pipe_mnt);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index d2e38dc6172c..3f65a4fa72ed 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -55,6 +55,11 @@ struct qstr {
 
 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
 
+extern const char empty_string[];
+extern const struct qstr empty_name;
+extern const char slash_string[];
+extern const struct qstr slash_name;
+
 struct dentry_stat_t {
 	long nr_dentry;
 	long nr_unused;

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Thread

[RFC][PATCH 00/14] VFS: Introduce superblock configuration context David Howells <dhowells@redhat.com> - 2017-05-10 18:20 +0200
  [PATCH 01/14] Provide a function to create a NUL-terminated string  from unterminated data David Howells <dhowells@redhat.com> - 2017-05-10 18:20 +0200
  [PATCH 07/14] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
    Re: [PATCH 07/14] Implement fsopen() to prepare for a mount Sargun Dhillon <sargun@sargun.me> - 2017-05-11 00:10 +0200
      Re: [PATCH 07/14] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-11 16:40 +0200
    Re: [PATCH 07/14] Implement fsopen() to prepare for a mount Jeff Layton <jlayton@redhat.com> - 2017-05-11 16:40 +0200
  [PATCH 08/14] Implement fsmount() to effect a pre-configured mount David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 11/14] proc: Add superblock config support to procfs David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 13/14] Support legacy filesystems David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 03/14] VFS: Make get_mnt_ns() return the namespace David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 05/14] VFS: Provide empty name qstr David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 02/14] Clean up whitespace in fs/namespace.c David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 10/14] procfs: Move proc_fill_super() to fs/proc/root.c David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 09/14] Sample program for driving fsopen/fsmount David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 04/14] VFS: Make get_filesystem() return the affected  filesystem David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  Re: [PATCH 06/14] VFS: Introduce a superblock configuration context Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-11 09:30 +0200
  Re: [PATCH 14/14] Add commands to create or update a superblock Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-11 09:40 +0200
    Re: [PATCH 14/14] Add commands to create or update a superblock Miklos Szeredi <mszeredi@redhat.com> - 2017-05-11 10:20 +0200

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