[PATCH v4 08/54] convert ramfs and tmpfs

[Al Viro <viro@zeniv.linux.org.uk>]

Quite a bit is already done by infrastructure changes (simple_link(),
simple_unlink()) - all that is left is replacing d_instantiate() +
pinning dget() (in ->symlink() and ->mknod()) with d_make_persistent(),
and, in case of shmem, using simple_unlink() and simple_link() in
->unlink() and ->link() resp., instead of open-coding those there.
Since d_make_persistent() accepts (and hashes) unhashed ones, shmem
situation gets simpler - we no longer care whether ->lookup() has hashed
the sucker.

With that done, we don't need kill_litter_super() for these filesystems
anymore - by the umount time all remaining dentries will be marked
persistent and kill_litter_super() will boil down to call of
kill_anon_super().

The same goes for devtmpfs and rootfs - they are handled by
ramfs or by shmem, depending upon config.

NB: strictly speaking, both devtmpfs and rootfs ought to use
ramfs_kill_sb() if they end up using ramfs; that's a separate
story and the only impact of "just use kill_{litter,anon}_super()"
is that we fail to free their sb->s_fs_info... on reboot.
That's orthogonal to the changes in this series - kill_litter_super()
is identical to kill_anon_super() for those at this point.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/base/devtmpfs.c |  2 +-
 fs/ramfs/inode.c        |  8 +++-----
 init/do_mounts.c        |  2 +-
 mm/shmem.c              | 38 ++++++++------------------------------
 4 files changed, 13 insertions(+), 37 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 9d4e46ad8352..a63b0ff0c432 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -70,7 +70,7 @@ static struct file_system_type internal_fs_type = {
 #else
 	.init_fs_context = ramfs_init_fs_context,
 #endif
-	.kill_sb = kill_litter_super,
+	.kill_sb = kill_anon_super,
 };
 
 /* Simply take a ref on the existing mount */
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 41f9995da7ca..505d10a0cb36 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -110,8 +110,7 @@ ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
 			goto out;
 		}
 
-		d_instantiate(dentry, inode);
-		dget(dentry);	/* Extra count - pin the dentry in core */
+		d_make_persistent(dentry, inode);
 		error = 0;
 		inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	}
@@ -154,8 +153,7 @@ static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 
 		error = page_symlink(inode, symname, l);
 		if (!error) {
-			d_instantiate(dentry, inode);
-			dget(dentry);
+			d_make_persistent(dentry, inode);
 			inode_set_mtime_to_ts(dir,
 					      inode_set_ctime_current(dir));
 		} else
@@ -313,7 +311,7 @@ int ramfs_init_fs_context(struct fs_context *fc)
 void ramfs_kill_sb(struct super_block *sb)
 {
 	kfree(sb->s_fs_info);
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 }
 
 static struct file_system_type ramfs_fs_type = {
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 6af29da8889e..810878fb55b6 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -507,7 +507,7 @@ static int rootfs_init_fs_context(struct fs_context *fc)
 struct file_system_type rootfs_fs_type = {
 	.name		= "rootfs",
 	.init_fs_context = rootfs_init_fs_context,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 };
 
 void __init init_rootfs(void)
diff --git a/mm/shmem.c b/mm/shmem.c
index b9081b817d28..a38f71519813 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3858,12 +3858,7 @@ shmem_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	inode_inc_iversion(dir);
 
-	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
-		d_add(dentry, inode);
-	else
-		d_instantiate(dentry, inode);
-
-	dget(dentry); /* Extra count - pin the dentry in core */
+	d_make_persistent(dentry, inode);
 	return error;
 
 out_iput:
@@ -3924,7 +3919,7 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir,
 		      struct dentry *dentry)
 {
 	struct inode *inode = d_inode(old_dentry);
-	int ret = 0;
+	int ret;
 
 	/*
 	 * No ordinary (disk based) filesystem counts links as inodes;
@@ -3936,29 +3931,19 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir,
 	if (inode->i_nlink) {
 		ret = shmem_reserve_inode(inode->i_sb, NULL);
 		if (ret)
-			goto out;
+			return ret;
 	}
 
 	ret = simple_offset_add(shmem_get_offset_ctx(dir), dentry);
 	if (ret) {
 		if (inode->i_nlink)
 			shmem_free_inode(inode->i_sb, 0);
-		goto out;
+		return ret;
 	}
 
 	dir->i_size += BOGO_DIRENT_SIZE;
-	inode_set_mtime_to_ts(dir,
-			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
 	inode_inc_iversion(dir);
-	inc_nlink(inode);
-	ihold(inode);	/* New dentry reference */
-	dget(dentry);	/* Extra pinning count for the created dentry */
-	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
-		d_add(dentry, inode);
-	else
-		d_instantiate(dentry, inode);
-out:
-	return ret;
+	return simple_link(old_dentry, dir, dentry);
 }
 
 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
@@ -3971,11 +3956,8 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry)
 	simple_offset_remove(shmem_get_offset_ctx(dir), dentry);
 
 	dir->i_size -= BOGO_DIRENT_SIZE;
-	inode_set_mtime_to_ts(dir,
-			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
 	inode_inc_iversion(dir);
-	drop_nlink(inode);
-	dput(dentry);	/* Undo the count from "create" - does all the work */
+	simple_unlink(dir, dentry);
 
 	/*
 	 * For now, VFS can't deal with case-insensitive negative dentries, so
@@ -4130,11 +4112,7 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
 	dir->i_size += BOGO_DIRENT_SIZE;
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	inode_inc_iversion(dir);
-	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
-		d_add(dentry, inode);
-	else
-		d_instantiate(dentry, inode);
-	dget(dentry);
+	d_make_persistent(dentry, inode);
 	return 0;
 
 out_remove_offset:
@@ -5334,7 +5312,7 @@ static struct file_system_type shmem_fs_type = {
 #ifdef CONFIG_TMPFS
 	.parameters	= shmem_fs_parameters,
 #endif
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP | FS_MGTIME,
 };
 
-- 
2.47.3