[PATCH 06/39] convert ramfs and tmpfs
From: Al Viro <viro@zeniv.linux.org.uk>
Date: 2025-09-20 07:48:02
Also in:
linux-efi, linux-fsdevel, linux-mm, linux-usb, ocfs2-devel
Subsystem:
driver core, kobjects, debugfs and sysfs, filesystems (vfs and infrastructure), memory management, the rest, tmpfs (shmem filesystem) · Maintainers:
Greg Kroah-Hartman, "Rafael J. Wysocki", Danilo Krummrich, Alexander Viro, Christian Brauner, Andrew Morton, Linus Torvalds, Hugh Dickins
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, unpinning dput() in ->unlink() with d_make_discardable().
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 | 23 +++++------------------
4 files changed, 10 insertions(+), 25 deletions(-)
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 31bfb3194b4c..30b5ae8d79cf 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 f8874c3b8c1e..3cc36b1c60b3 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 e2c76a30802b..2d5832a1e67a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c@@ -3922,12 +3922,7 @@ 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:
@@ -4016,11 +4011,7 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir, 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); + d_make_persistent(dentry, inode); out: return ret; }
@@ -4039,7 +4030,7 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry) 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 */ + d_make_discardable(dentry); /* * For now, VFS can't deal with case-insensitive negative dentries, so
@@ -4194,11 +4185,7 @@ 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:
@@ -5395,7 +5382,7 @@ 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