[PATCH v3 08/50] convert ramfs and tmpfs

Al Viro
2025-11-11T06:55:27Z

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