replace ->follow_link() with new method that could stay in RCU mode

new method: ->get_link(); replacement of ->follow_link(). The differences are: * inode and dentry are passed separately * might be called both in RCU and non-RCU mode; the former is indicated by passing it a NULL dentry. * when called that way it isn't allowed to block and should return ERR_PTR(-ECHILD) if it needs to be called in non-RCU mode. It's a flagday change - the old method is gone, all in-tree instances converted. Conversion isn't hard; said that, so far very few instances do not immediately bail out when called in RCU mode. That'll change in the next commits. Signed-off-by: Al Viro <[email protected]>
niw · Dec 9, 2015 · 6b25539 · 6b25539
1 parent 21fc61c
commit 6b25539
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Showing 45 changed files with 234 additions and 132 deletions.
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
@@ -50,7 +50,7 @@ prototypes:
 	int (*rename2) (struct inode *, struct dentry *,
 			struct inode *, struct dentry *, unsigned int);
 	int (*readlink) (struct dentry *, char __user *,int);
-	const char *(*follow_link) (struct dentry *, void **);
+	const char *(*get_link) (struct dentry *, struct inode *, void **);
 	void (*put_link) (struct inode *, void *);
 	void (*truncate) (struct inode *);
 	int (*permission) (struct inode *, int, unsigned int);
@@ -83,7 +83,7 @@ rmdir:		yes (both)	(see below)
 rename:		yes (all)	(see below)
 rename2:	yes (all)	(see below)
 readlink:	no
-follow_link:	no
+get_link:	no
 put_link:	no
 setattr:	yes
 permission:	no (may not block if called in rcu-walk mode)

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
@@ -509,3 +509,9 @@ in your dentry operations instead.
 	any symlink that might use page_follow_link_light/page_put_link() must
 	have inode_nohighmem(inode) called before anything might start playing with
 	its pagecache.
+--
+[mandatory]
+	->follow_link() is replaced with ->get_link(); same API, except that
+		* ->get_link() gets inode as a separate argument
+		* ->get_link() may be called in RCU mode - in that case NULL
+		  dentry is passed
diff --git a/drivers/staging/lustre/lustre/llite/symlink.c b/drivers/staging/lustre/lustre/llite/symlink.c
@@ -118,12 +118,14 @@ static int ll_readlink_internal(struct inode *inode,
 	return rc;
 }
 
-static const char *ll_follow_link(struct dentry *dentry, void **cookie)
+static const char *ll_get_link(struct dentry *dentry,
+			       struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(dentry);
 	struct ptlrpc_request *request = NULL;
 	int rc;
 	char *symname = NULL;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
 
 	CDEBUG(D_VFSTRACE, "VFS Op\n");
 	ll_inode_size_lock(inode);
@@ -149,7 +151,7 @@ static void ll_put_link(struct inode *unused, void *cookie)
 struct inode_operations ll_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.setattr	= ll_setattr,
-	.follow_link	= ll_follow_link,
+	.get_link	= ll_get_link,
 	.put_link	= ll_put_link,
 	.getattr	= ll_getattr,
 	.permission	= ll_inode_permission,

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
@@ -1223,18 +1223,25 @@ ino_t v9fs_qid2ino(struct p9_qid *qid)
 }
 
 /**
- * v9fs_vfs_follow_link - follow a symlink path
+ * v9fs_vfs_get_link - follow a symlink path
  * @dentry: dentry for symlink
+ * @inode: inode for symlink
  * @cookie: place to pass the data to put_link()
  */
 
-static const char *v9fs_vfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *v9fs_vfs_get_link(struct dentry *dentry,
+				     struct inode *inode, void **cookie)
 {
-	struct v9fs_session_info *v9ses = v9fs_dentry2v9ses(dentry);
-	struct p9_fid *fid = v9fs_fid_lookup(dentry);
+	struct v9fs_session_info *v9ses;
+	struct p9_fid *fid;
 	struct p9_wstat *st;
 	char *res;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	v9ses = v9fs_dentry2v9ses(dentry);
+	fid = v9fs_fid_lookup(dentry);
 	p9_debug(P9_DEBUG_VFS, "%pd\n", dentry);
 
 	if (IS_ERR(fid))
@@ -1452,7 +1459,7 @@ static const struct inode_operations v9fs_file_inode_operations = {
 
 static const struct inode_operations v9fs_symlink_inode_operations = {
 	.readlink = generic_readlink,
-	.follow_link = v9fs_vfs_follow_link,
+	.get_link = v9fs_vfs_get_link,
 	.put_link = kfree_put_link,
 	.getattr = v9fs_vfs_getattr,
 	.setattr = v9fs_vfs_setattr,

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
@@ -899,20 +899,26 @@ v9fs_vfs_mknod_dotl(struct inode *dir, struct dentry *dentry, umode_t omode,
 }
 
 /**
- * v9fs_vfs_follow_link_dotl - follow a symlink path
+ * v9fs_vfs_get_link_dotl - follow a symlink path
  * @dentry: dentry for symlink
+ * @inode: inode for symlink
  * @cookie: place to pass the data to put_link()
  */
 
 static const char *
-v9fs_vfs_follow_link_dotl(struct dentry *dentry, void **cookie)
+v9fs_vfs_get_link_dotl(struct dentry *dentry,
+		       struct inode *inode, void **cookie)
 {
-	struct p9_fid *fid = v9fs_fid_lookup(dentry);
+	struct p9_fid *fid;
 	char *target;
 	int retval;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	p9_debug(P9_DEBUG_VFS, "%pd\n", dentry);
 
+	fid = v9fs_fid_lookup(dentry);
 	if (IS_ERR(fid))
 		return ERR_CAST(fid);
 	retval = p9_client_readlink(fid, &target);
@@ -984,7 +990,7 @@ const struct inode_operations v9fs_file_inode_operations_dotl = {
 
 const struct inode_operations v9fs_symlink_inode_operations_dotl = {
 	.readlink = generic_readlink,
-	.follow_link = v9fs_vfs_follow_link_dotl,
+	.get_link = v9fs_vfs_get_link_dotl,
 	.put_link = kfree_put_link,
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,

diff --git a/fs/affs/symlink.c b/fs/affs/symlink.c
@@ -20,7 +20,7 @@ static int affs_symlink_readpage(struct file *file, struct page *page)
 	char			 c;
 	char			 lc;
 
-	pr_debug("follow_link(ino=%lu)\n", inode->i_ino);
+	pr_debug("get_link(ino=%lu)\n", inode->i_ino);
 
 	bh = affs_bread(inode->i_sb, inode->i_ino);
 	if (!bh)
@@ -71,7 +71,7 @@ const struct address_space_operations affs_symlink_aops = {
 
 const struct inode_operations affs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= affs_notify_change,
 };
diff --git a/fs/autofs4/symlink.c b/fs/autofs4/symlink.c
@@ -12,16 +12,21 @@
 
 #include "autofs_i.h"
 
-static const char *autofs4_follow_link(struct dentry *dentry, void **cookie)
+static const char *autofs4_get_link(struct dentry *dentry,
+				    struct inode *inode, void **cookie)
 {
-	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
-	struct autofs_info *ino = autofs4_dentry_ino(dentry);
+	struct autofs_sb_info *sbi;
+	struct autofs_info *ino;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	sbi = autofs4_sbi(dentry->d_sb);
+	ino = autofs4_dentry_ino(dentry);
 	if (ino && !autofs4_oz_mode(sbi))
 		ino->last_used = jiffies;
 	return d_inode(dentry)->i_private;
 }
 
 const struct inode_operations autofs4_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= autofs4_follow_link
+	.get_link	= autofs4_get_link
 };
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
@@ -10096,7 +10096,7 @@ static const struct inode_operations btrfs_special_inode_operations = {
 };
 static const struct inode_operations btrfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.getattr	= btrfs_getattr,
 	.setattr	= btrfs_setattr,

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
@@ -1756,7 +1756,7 @@ void __ceph_do_pending_vmtruncate(struct inode *inode)
  */
 static const struct inode_operations ceph_symlink_iops = {
 	.readlink = generic_readlink,
-	.follow_link = simple_follow_link,
+	.get_link = simple_get_link,
 	.setattr = ceph_setattr,
 	.getattr = ceph_getattr,
 	.setxattr = ceph_setxattr,

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
@@ -900,7 +900,7 @@ const struct inode_operations cifs_file_inode_ops = {
 
 const struct inode_operations cifs_symlink_inode_ops = {
 	.readlink = generic_readlink,
-	.follow_link = cifs_follow_link,
+	.get_link = cifs_get_link,
 	.put_link = kfree_put_link,
 	.permission = cifs_permission,
 	/* BB add the following two eventually */

diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
@@ -120,9 +120,7 @@ extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
 #endif
 
 /* Functions related to symlinks */
-extern const char *cifs_follow_link(struct dentry *direntry, void **cookie);
-extern int cifs_readlink(struct dentry *direntry, char __user *buffer,
-			 int buflen);
+extern const char *cifs_get_link(struct dentry *, struct inode *, void **);
 extern int cifs_symlink(struct inode *inode, struct dentry *direntry,
 			const char *symname);
 extern int	cifs_removexattr(struct dentry *, const char *);

diff --git a/fs/cifs/link.c b/fs/cifs/link.c
@@ -627,9 +627,8 @@ cifs_hardlink(struct dentry *old_file, struct inode *inode,
 }
 
 const char *
-cifs_follow_link(struct dentry *direntry, void **cookie)
+cifs_get_link(struct dentry *direntry, struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(direntry);
 	int rc = -ENOMEM;
 	unsigned int xid;
 	char *full_path = NULL;
@@ -639,6 +638,9 @@ cifs_follow_link(struct dentry *direntry, void **cookie)
 	struct cifs_tcon *tcon;
 	struct TCP_Server_Info *server;
 
+	if (!direntry)
+		return ERR_PTR(-ECHILD);
+
 	xid = get_xid();
 
 	tlink = cifs_sb_tlink(cifs_sb);

diff --git a/fs/coda/cnode.c b/fs/coda/cnode.c
@@ -18,7 +18,7 @@ static inline int coda_fideq(struct CodaFid *fid1, struct CodaFid *fid2)
 
 static const struct inode_operations coda_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= coda_setattr,
 };

diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
@@ -279,11 +279,16 @@ static int configfs_getlink(struct dentry *dentry, char * path)
 
 }
 
-static const char *configfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *configfs_get_link(struct dentry *dentry,
+				     struct inode *inode, void **cookie)
 {
-	unsigned long page = get_zeroed_page(GFP_KERNEL);
+	unsigned long page;
 	int error;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	page = get_zeroed_page(GFP_KERNEL);
 	if (!page)
 		return ERR_PTR(-ENOMEM);
 
@@ -297,7 +302,7 @@ static const char *configfs_follow_link(struct dentry *dentry, void **cookie)
 }
 
 const struct inode_operations configfs_symlink_inode_operations = {
-	.follow_link = configfs_follow_link,
+	.get_link = configfs_get_link,
 	.readlink = generic_readlink,
 	.put_link = free_page_put_link,
 	.setattr = configfs_setattr,

diff --git a/fs/dcache.c b/fs/dcache.c
@@ -1734,7 +1734,7 @@ static unsigned d_flags_for_inode(struct inode *inode)
 	}
 
 	if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
-		if (unlikely(inode->i_op->follow_link)) {
+		if (unlikely(inode->i_op->get_link)) {
 			add_flags = DCACHE_SYMLINK_TYPE;
 			goto type_determined;
 		}

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
@@ -674,10 +674,16 @@ static char *ecryptfs_readlink_lower(struct dentry *dentry, size_t *bufsiz)
 	return rc ? ERR_PTR(rc) : buf;
 }
 
-static const char *ecryptfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *ecryptfs_get_link(struct dentry *dentry,
+				     struct inode *inode, void **cookie)
 {
 	size_t len;
-	char *buf = ecryptfs_readlink_lower(dentry, &len);
+	char *buf;
+
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	buf = ecryptfs_readlink_lower(dentry, &len);
 	if (IS_ERR(buf))
 		return buf;
 	fsstack_copy_attr_atime(d_inode(dentry),
@@ -1095,7 +1101,7 @@ static int ecryptfs_removexattr(struct dentry *dentry, const char *name)
 
 const struct inode_operations ecryptfs_symlink_iops = {
 	.readlink = generic_readlink,
-	.follow_link = ecryptfs_follow_link,
+	.get_link = ecryptfs_get_link,
 	.put_link = kfree_put_link,
 	.permission = ecryptfs_permission,
 	.setattr = ecryptfs_setattr,

diff --git a/fs/ext2/symlink.c b/fs/ext2/symlink.c
@@ -22,7 +22,7 @@
 
 const struct inode_operations ext2_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= ext2_setattr,
 #ifdef CONFIG_EXT2_FS_XATTR
@@ -35,7 +35,7 @@ const struct inode_operations ext2_symlink_inode_operations = {
 
 const struct inode_operations ext2_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= simple_follow_link,
+	.get_link	= simple_get_link,
 	.setattr	= ext2_setattr,
 #ifdef CONFIG_EXT2_FS_XATTR
 	.setxattr	= generic_setxattr,

diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
@@ -23,17 +23,20 @@
 #include "xattr.h"
 
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
-static const char *ext4_encrypted_follow_link(struct dentry *dentry, void **cookie)
+static const char *ext4_encrypted_get_link(struct dentry *dentry,
+					   struct inode *inode, void **cookie)
 {
 	struct page *cpage = NULL;
 	char *caddr, *paddr = NULL;
 	struct ext4_str cstr, pstr;
-	struct inode *inode = d_inode(dentry);
 	struct ext4_encrypted_symlink_data *sd;
 	loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
 	int res;
 	u32 plen, max_size = inode->i_sb->s_blocksize;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	res = ext4_get_encryption_info(inode);
 	if (res)
 		return ERR_PTR(res);
@@ -87,7 +90,7 @@ static const char *ext4_encrypted_follow_link(struct dentry *dentry, void **cook
 
 const struct inode_operations ext4_encrypted_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link    = ext4_encrypted_follow_link,
+	.get_link	= ext4_encrypted_get_link,
 	.put_link       = kfree_put_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
@@ -99,7 +102,7 @@ const struct inode_operations ext4_encrypted_symlink_inode_operations = {
 
 const struct inode_operations ext4_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
@@ -110,7 +113,7 @@ const struct inode_operations ext4_symlink_inode_operations = {
 
 const struct inode_operations ext4_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link    = simple_follow_link,
+	.get_link	= simple_get_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
 	.getxattr	= generic_getxattr,