[PATCH v2 0/4] super: retire sget()

[PATCH v2 0/4] super: retire sget()

[Christian Brauner]

CIFS plus the two ext4 KUnit tests (extents-test, mballoc-test) were the
last in-tree callers, and all three convert cleanly to sget_fc(). That
lets sget() and its prototype come out, taking ~60 lines that only
existed to be kept in lockstep with sget_fc() on every publish-path
change.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
Changes in v2:
- Move some changes into a separate series.
- Link to v1: https://patch.msgid.link/20260526-work-sget-v1-0-263f7025cedd@kernel.org

---
Christian Brauner (4):
      ext4: convert extents KUnit test to sget_fc()
      ext4: convert mballoc KUnit test to sget_fc()
      smb: client: convert cifs_smb3_do_mount() to sget_fc()
      fs: retire sget()

 fs/btrfs/super.c           |  2 +-
 fs/ext4/extents-test.c     | 22 +++++++++++---
 fs/ext4/mballoc-test.c     | 17 +++++++++--
 fs/smb/client/cifsfs.c     | 43 +++++++++++++++++-----------
 fs/smb/client/cifsfs.h     |  3 +-
 fs/smb/client/cifsproto.h  |  3 +-
 fs/smb/client/connect.c    |  5 ++--
 fs/smb/client/fs_context.c |  2 +-
 fs/super.c                 | 71 ++++------------------------------------------
 include/linux/fs.h         |  4 ---
 10 files changed, 73 insertions(+), 99 deletions(-)
---
base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
change-id: 20260526-work-sget-6bc80b96cba5

[PATCH v2 1/4] ext4: convert extents KUnit test to sget_fc()

[Christian Brauner]

The extents KUnit test uses sget() to get an initialized superblock for
its fake file_system_type. sget() predates fs_context and we want to
retire it. Switch this caller over to sget_fc().

Add a no-op ext_init_fs_context() so fs_context_for_mount() has
something to call on the fake fs_type. ext_set() now takes a struct
fs_context * (still a no-op). extents_kunit_init() allocates the fc,
hands it to sget_fc() and drops the fc reference once the sb is
published. sget_fc() does not retain a pointer to it.

No functional change for the test.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/ext4/extents-test.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/extents-test.c b/fs/ext4/extents-test.c
index 6b53a3f39fcd..bd7795a82607 100644
--- a/fs/ext4/extents-test.c
+++ b/fs/ext4/extents-test.c
@@ -37,6 +37,7 @@
 
 #include <kunit/test.h>
 #include <kunit/static_stub.h>
+#include <linux/fs_context.h>
 #include <linux/gfp_types.h>
 #include <linux/stddef.h>
 
@@ -130,14 +131,20 @@ static void ext_kill_sb(struct super_block *sb)
 	generic_shutdown_super(sb);
 }
 
-static int ext_set(struct super_block *sb, void *data)
+static int ext_init_fs_context(struct fs_context *fc)
+{
+	return 0;
+}
+
+static int ext_set(struct super_block *sb, struct fs_context *fc)
 {
 	return 0;
 }
 
 static struct file_system_type ext_fs_type = {
-	.name = "extents test",
-	.kill_sb = ext_kill_sb,
+	.name		 = "extents test",
+	.init_fs_context = ext_init_fs_context,
+	.kill_sb	 = ext_kill_sb,
 };
 
 static void extents_kunit_exit(struct kunit *test)
@@ -223,6 +230,7 @@ static int extents_kunit_init(struct kunit *test)
 	struct ext4_inode_info *ei;
 	struct inode *inode;
 	struct super_block *sb;
+	struct fs_context *fc;
 	struct ext4_sb_info *sbi = NULL;
 	struct kunit_ext_test_param *param =
 		(struct kunit_ext_test_param *)(test->param_value);
@@ -232,7 +240,13 @@ static int extents_kunit_init(struct kunit *test)
 	if (sbi == NULL)
 		return -ENOMEM;
 
-	sb = sget(&ext_fs_type, NULL, ext_set, 0, NULL);
+	fc = fs_context_for_mount(&ext_fs_type, 0);
+	if (IS_ERR(fc)) {
+		kfree(sbi);
+		return PTR_ERR(fc);
+	}
+	sb = sget_fc(fc, NULL, ext_set);
+	put_fs_context(fc);
 	if (IS_ERR(sb)) {
 		kfree(sbi);
 		return PTR_ERR(sb);

-- 
2.47.3

[PATCH v2 2/4] ext4: convert mballoc KUnit test to sget_fc()

[Christian Brauner]

Same treatment as the extents KUnit test. The mballoc test uses sget()
as a thin "give me an initialized superblock" wrapper for a fake
file_system_type. Move it onto sget_fc() so sget() can go away.

Add a no-op mbt_init_fs_context() so fs_context_for_mount() has
something to call on the fake fs_type. mbt_set() now takes a struct
fs_context * (still a no-op). mbt_ext4_alloc_super_block() allocates
the fc, hands it to sget_fc() and drops the fc reference once the sb
is published.

No functional change.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/ext4/mballoc-test.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/mballoc-test.c b/fs/ext4/mballoc-test.c
index 90ed505fa4b1..d90da44aadbd 100644
--- a/fs/ext4/mballoc-test.c
+++ b/fs/ext4/mballoc-test.c
@@ -5,6 +5,7 @@
 
 #include <kunit/test.h>
 #include <kunit/static_stub.h>
+#include <linux/fs_context.h>
 #include <linux/random.h>
 
 #include "ext4.h"
@@ -63,8 +64,14 @@ static void mbt_kill_sb(struct super_block *sb)
 	generic_shutdown_super(sb);
 }
 
+static int mbt_init_fs_context(struct fs_context *fc)
+{
+	return 0;
+}
+
 static struct file_system_type mbt_fs_type = {
 	.name			= "mballoc test",
+	.init_fs_context	= mbt_init_fs_context,
 	.kill_sb		= mbt_kill_sb,
 };
 
@@ -127,7 +134,7 @@ static void mbt_mb_release(struct super_block *sb)
 	kfree(sb->s_bdev);
 }
 
-static int mbt_set(struct super_block *sb, void *data)
+static int mbt_set(struct super_block *sb, struct fs_context *fc)
 {
 	return 0;
 }
@@ -136,13 +143,19 @@ static struct super_block *mbt_ext4_alloc_super_block(void)
 {
 	struct mbt_ext4_super_block *fsb;
 	struct super_block *sb;
+	struct fs_context *fc;
 	struct ext4_sb_info *sbi;
 
 	fsb = kzalloc_obj(*fsb);
 	if (fsb == NULL)
 		return NULL;
 
-	sb = sget(&mbt_fs_type, NULL, mbt_set, 0, NULL);
+	fc = fs_context_for_mount(&mbt_fs_type, 0);
+	if (IS_ERR(fc))
+		goto out;
+
+	sb = sget_fc(fc, NULL, mbt_set);
+	put_fs_context(fc);
 	if (IS_ERR(sb))
 		goto out;
 

-- 
2.47.3

[PATCH v2 3/4] smb: client: convert cifs_smb3_do_mount() to sget_fc()

[Christian Brauner]

The CIFS mount path already runs through fs_context: smb3_get_tree()
calls smb3_get_tree_common() with a struct fs_context * in hand. But
the fc is dropped on the way to sget(). Plumb it through to sget_fc()
so the legacy sget() interface can go.

cifs_smb3_do_mount() now takes (struct fs_context *, struct
smb3_fs_context *). The old (fs_type, flags) pair is reconstructed
from fc->fs_type and fc->sb_flags. The flags argument was always
passed as 0 by the sole caller anyway. The cifs_dbg diagnostic now
prints fc->sb_flags directly.

cifs_match_super() and cifs_set_super() were the two void-data
callbacks for sget(). The match callback now takes
(struct super_block *, struct fs_context *) and reads struct
cifs_mnt_data out of fc->sget_key. The set callback is gone entirely:
sget_fc() pre-populates sb->s_fs_info from fc->s_fs_info before
invoking set() so set_anon_super_fc() (which just allocates an anon
bdev) is sufficient.

Before sget_fc() we stash cifs_sb in fc->s_fs_info, the per-mount data
in fc->sget_key and force fc->sb_flags to SB_NODIRATIME | SB_NOATIME
to reproduce the previous hard-coded behaviour (alloc_super() reads
fc->sb_flags). The original sb_flags is saved and restored around the
call so the rest of the mount path sees the same fc semantics as
before.

mnt_data.flags keeps its historical value of 0 so the CIFS_MS_MASK
comparison in compare_mount_options() returns the same (always-equal)
result.

No functional change. With this in place sget() has no remaining CIFS
caller.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/smb/client/cifsfs.c     | 43 ++++++++++++++++++++++++++-----------------
 fs/smb/client/cifsfs.h     |  3 ++-
 fs/smb/client/cifsproto.h  |  3 ++-
 fs/smb/client/connect.c    |  5 +++--
 fs/smb/client/fs_context.c |  2 +-
 5 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index 9f76b0347fa9..d5074e3fbb85 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -12,6 +12,7 @@
 
 #include <linux/module.h>
 #include <linux/fs.h>
+#include <linux/fs_context.h>
 #include <linux/filelock.h>
 #include <linux/mount.h>
 #include <linux/slab.h>
@@ -966,26 +967,19 @@ cifs_get_root(struct smb3_fs_context *ctx, struct super_block *sb)
 	return dentry;
 }
 
-static int cifs_set_super(struct super_block *sb, void *data)
-{
-	struct cifs_mnt_data *mnt_data = data;
-	sb->s_fs_info = mnt_data->cifs_sb;
-	return set_anon_super(sb, NULL);
-}
-
 struct dentry *
-cifs_smb3_do_mount(struct file_system_type *fs_type,
-	      int flags, struct smb3_fs_context *old_ctx)
+cifs_smb3_do_mount(struct fs_context *fc, struct smb3_fs_context *old_ctx)
 {
 	struct cifs_mnt_data mnt_data;
 	struct cifs_sb_info *cifs_sb;
 	struct super_block *sb;
 	struct dentry *root;
+	unsigned int saved_sb_flags;
 	int rc;
 
 	if (cifsFYI) {
-		cifs_dbg(FYI, "%s: devname=%s flags=0x%x\n", __func__,
-			 old_ctx->source, flags);
+		cifs_dbg(FYI, "%s: devname=%s sb_flags=0x%x\n", __func__,
+			 old_ctx->source, fc->sb_flags);
 	} else {
 		cifs_info("Attempting to mount %s\n", old_ctx->source);
 	}
@@ -1012,7 +1006,7 @@ cifs_smb3_do_mount(struct file_system_type *fs_type,
 
 	rc = cifs_mount(cifs_sb, cifs_sb->ctx);
 	if (rc) {
-		if (!(flags & SB_SILENT))
+		if (!(fc->sb_flags & SB_SILENT))
 			cifs_dbg(VFS, "cifs_mount failed w/return code = %d\n",
 				 rc);
 		root = ERR_PTR(rc);
@@ -1021,12 +1015,27 @@ cifs_smb3_do_mount(struct file_system_type *fs_type,
 
 	mnt_data.ctx = cifs_sb->ctx;
 	mnt_data.cifs_sb = cifs_sb;
-	mnt_data.flags = flags;
+	mnt_data.flags = 0;
 
-	/* BB should we make this contingent on mount parm? */
-	flags |= SB_NODIRATIME | SB_NOATIME;
-
-	sb = sget(fs_type, cifs_match_super, cifs_set_super, flags, &mnt_data);
+	/*
+	 * sb->s_flags is set from fc->sb_flags by alloc_super(). CIFS has
+	 * historically forced SB_NODIRATIME | SB_NOATIME on every mount and
+	 * ignored the caller-supplied SB_* flags. Preserve that behaviour by
+	 * overriding fc->sb_flags around the sget_fc() call.
+	 *
+	 * Hand cifs_sb to sget_fc() via fc->s_fs_info; sget_fc() copies it
+	 * onto sb->s_fs_info before running set() and clears fc->s_fs_info
+	 * on successful publish. Pass the rest of the per-mount context to
+	 * cifs_match_super() through fc->sget_key.
+	 */
+	saved_sb_flags = fc->sb_flags;
+	fc->sb_flags = SB_NODIRATIME | SB_NOATIME;
+	fc->s_fs_info = cifs_sb;
+	fc->sget_key = &mnt_data;
+	sb = sget_fc(fc, cifs_match_super, set_anon_super_fc);
+	fc->sget_key = NULL;
+	fc->s_fs_info = NULL;
+	fc->sb_flags = saved_sb_flags;
 	if (IS_ERR(sb)) {
 		cifs_umount(cifs_sb);
 		return ERR_CAST(sb);
diff --git a/fs/smb/client/cifsfs.h b/fs/smb/client/cifsfs.h
index c455b15f2778..0a93f48924a5 100644
--- a/fs/smb/client/cifsfs.h
+++ b/fs/smb/client/cifsfs.h
@@ -144,8 +144,9 @@ ssize_t cifs_file_copychunk_range(unsigned int xid, struct file *src_file,
 long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg);
 void cifs_setsize(struct inode *inode, loff_t offset);
 
+struct fs_context;
 struct smb3_fs_context;
-struct dentry *cifs_smb3_do_mount(struct file_system_type *fs_type, int flags,
+struct dentry *cifs_smb3_do_mount(struct fs_context *fc,
 				  struct smb3_fs_context *old_ctx);
 
 char *cifs_silly_fullpath(struct dentry *dentry);
diff --git a/fs/smb/client/cifsproto.h b/fs/smb/client/cifsproto.h
index 4a25afda9448..a39572cbaadb 100644
--- a/fs/smb/client/cifsproto.h
+++ b/fs/smb/client/cifsproto.h
@@ -19,6 +19,7 @@
 struct statfs;
 struct smb_rqst;
 struct smb3_fs_context;
+struct fs_context;
 
 /*
  *****************************************************************
@@ -236,7 +237,7 @@ void cifs_mount_put_conns(struct cifs_mount_ctx *mnt_ctx);
 int cifs_mount_get_session(struct cifs_mount_ctx *mnt_ctx);
 int cifs_is_path_remote(struct cifs_mount_ctx *mnt_ctx);
 int cifs_mount_get_tcon(struct cifs_mount_ctx *mnt_ctx);
-int cifs_match_super(struct super_block *sb, void *data);
+int cifs_match_super(struct super_block *sb, struct fs_context *fc);
 int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx);
 void cifs_umount(struct cifs_sb_info *cifs_sb);
 void cifs_mark_open_files_invalid(struct cifs_tcon *tcon);
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index dcde25da468d..79762e6bbe50 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -6,6 +6,7 @@
  *
  */
 #include <linux/fs.h>
+#include <linux/fs_context.h>
 #include <linux/net.h>
 #include <linux/string.h>
 #include <linux/sched/mm.h>
@@ -2991,9 +2992,9 @@ static int match_prepath(struct super_block *sb,
 }
 
 int
-cifs_match_super(struct super_block *sb, void *data)
+cifs_match_super(struct super_block *sb, struct fs_context *fc)
 {
-	struct cifs_mnt_data *mnt_data = data;
+	struct cifs_mnt_data *mnt_data = fc->sget_key;
 	struct smb3_fs_context *ctx;
 	struct cifs_sb_info *cifs_sb;
 	struct TCP_Server_Info *tcp_srv;
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index b9544eb0381b..6aba4e1c9c27 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -920,7 +920,7 @@ static int smb3_get_tree_common(struct fs_context *fc)
 	struct dentry *root;
 	int rc = 0;
 
-	root = cifs_smb3_do_mount(fc->fs_type, 0, ctx);
+	root = cifs_smb3_do_mount(fc, ctx);
 	if (IS_ERR(root))
 		return PTR_ERR(root);
 

-- 
2.47.3

[PATCH v2 4/4] fs: retire sget()

[Christian Brauner]

sget() and sget_fc() have lived side by side as near-duplicate
find-or-create-and-publish helpers for the legacy and fs_context mount
APIs. The three remaining in-tree callers (CIFS plus the ext4 extents
and mballoc KUnit tests) have all been moved to sget_fc(). Nothing
calls sget() anymore.

Delete sget() from fs/super.c and the prototype in <linux/fs.h>.
Update the two comments that referred to "sget()" or "sget{_fc}()" to
just say "sget_fc()".

This removes ~60 lines of code that only existed to be kept in
lockstep with sget_fc() on every superblock publish-path change.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/btrfs/super.c   |  2 +-
 fs/super.c         | 71 ++++--------------------------------------------------
 include/linux/fs.h |  4 ---
 3 files changed, 6 insertions(+), 71 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index b26aa9169e83..636154861d7c 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2052,7 +2052,7 @@ static int btrfs_get_tree_subvol(struct fs_context *fc)
 	 * then open_ctree will properly initialize the file system specific
 	 * settings later.  btrfs_init_fs_info initializes the static elements
 	 * of the fs_info (locks and such) to make cleanup easier if we find a
-	 * superblock with our given fs_devices later on at sget() time.
+	 * superblock with our given fs_devices later on at sget_fc() time.
 	 */
 	fs_info = kvzalloc_obj(struct btrfs_fs_info);
 	if (!fs_info)
diff --git a/fs/super.c b/fs/super.c
index 378e81efe643..5fe8cea9f8fe 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -328,7 +328,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	init_rwsem(&s->s_umount);
 	lockdep_set_class(&s->s_umount, &type->s_umount_key);
 	/*
-	 * sget() can have s_umount recursion.
+	 * sget_fc() can have s_umount recursion.
 	 *
 	 * When it cannot find a suitable sb, it allocates a new
 	 * one (this one), and tries again to find a suitable old
@@ -439,7 +439,7 @@ static void kill_super_notify(struct super_block *sb)
 
 	/*
 	 * Remove it from @fs_supers so it isn't found by new
-	 * sget{_fc}() walkers anymore. Any concurrent mounter still
+	 * sget_fc() walkers anymore. Any concurrent mounter still
 	 * managing to grab a temporary reference is guaranteed to
 	 * already see SB_DYING and will wait until we notify them about
 	 * SB_DEAD.
@@ -517,7 +517,7 @@ EXPORT_SYMBOL(deactivate_super);
  * @sb: superblock to acquire
  *
  * Acquire a temporary reference on a superblock and try to trade it for
- * an active reference. This is used in sget{_fc}() to wait for a
+ * an active reference. This is used in sget_fc() to wait for a
  * superblock to either become SB_BORN or for it to pass through
  * sb->kill() and be marked as SB_DEAD.
  *
@@ -673,11 +673,11 @@ void generic_shutdown_super(struct super_block *sb)
 	/*
 	 * Broadcast to everyone that grabbed a temporary reference to this
 	 * superblock before we removed it from @fs_supers that the superblock
-	 * is dying. Every walker of @fs_supers outside of sget{_fc}() will now
+	 * is dying. Every walker of @fs_supers outside of sget_fc() will now
 	 * discard this superblock and treat it as dead.
 	 *
 	 * We leave the superblock on @fs_supers so it can be found by
-	 * sget{_fc}() until we passed sb->kill_sb().
+	 * sget_fc() until we passed sb->kill_sb().
 	 */
 	super_wake(sb, SB_DYING);
 	super_unlock_excl(sb);
@@ -808,67 +808,6 @@ struct super_block *sget_fc(struct fs_context *fc,
 }
 EXPORT_SYMBOL(sget_fc);
 
-/**
- *	sget	-	find or create a superblock
- *	@type:	  filesystem type superblock should belong to
- *	@test:	  comparison callback
- *	@set:	  setup callback
- *	@flags:	  mount flags
- *	@data:	  argument to each of them
- */
-struct super_block *sget(struct file_system_type *type,
-			int (*test)(struct super_block *,void *),
-			int (*set)(struct super_block *,void *),
-			int flags,
-			void *data)
-{
-	struct user_namespace *user_ns = current_user_ns();
-	struct super_block *s = NULL;
-	struct super_block *old;
-	int err;
-
-retry:
-	spin_lock(&sb_lock);
-	if (test) {
-		hlist_for_each_entry(old, &type->fs_supers, s_instances) {
-			if (!test(old, data))
-				continue;
-			if (user_ns != old->s_user_ns) {
-				spin_unlock(&sb_lock);
-				destroy_unused_super(s);
-				return ERR_PTR(-EBUSY);
-			}
-			if (!grab_super(old))
-				goto retry;
-			destroy_unused_super(s);
-			return old;
-		}
-	}
-	if (!s) {
-		spin_unlock(&sb_lock);
-		s = alloc_super(type, flags, user_ns);
-		if (!s)
-			return ERR_PTR(-ENOMEM);
-		goto retry;
-	}
-
-	err = set(s, data);
-	if (err) {
-		spin_unlock(&sb_lock);
-		destroy_unused_super(s);
-		return ERR_PTR(err);
-	}
-	s->s_type = type;
-	strscpy(s->s_id, type->name, sizeof(s->s_id));
-	list_add_tail(&s->s_list, &super_blocks);
-	hlist_add_head(&s->s_instances, &type->fs_supers);
-	spin_unlock(&sb_lock);
-	get_filesystem(type);
-	shrinker_register(s->s_shrink);
-	return s;
-}
-EXPORT_SYMBOL(sget);
-
 void drop_super(struct super_block *sb)
 {
 	super_unlock_shared(sb);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 11559c513dfb..6dbe3218dc1e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2327,10 +2327,6 @@ void free_anon_bdev(dev_t);
 struct super_block *sget_fc(struct fs_context *fc,
 			    int (*test)(struct super_block *, struct fs_context *),
 			    int (*set)(struct super_block *, struct fs_context *));
-struct super_block *sget(struct file_system_type *type,
-			int (*test)(struct super_block *,void *),
-			int (*set)(struct super_block *,void *),
-			int flags, void *data);
 struct super_block *sget_dev(struct fs_context *fc, dev_t dev);
 
 /* Alas, no aliases. Too much hassle with bringing module.h everywhere */

-- 
2.47.3

Re: [PATCH v2 1/4] ext4: convert extents KUnit test to sget_fc()

[Jan Kara]

On Fri 29-05-26 10:43:40, Christian Brauner wrote:
> The extents KUnit test uses sget() to get an initialized superblock for
> its fake file_system_type. sget() predates fs_context and we want to
> retire it. Switch this caller over to sget_fc().
> 
> Add a no-op ext_init_fs_context() so fs_context_for_mount() has
> something to call on the fake fs_type. ext_set() now takes a struct
> fs_context * (still a no-op). extents_kunit_init() allocates the fc,
> hands it to sget_fc() and drops the fc reference once the sb is
> published. sget_fc() does not retain a pointer to it.
> 
> No functional change for the test.
> 
> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext4/extents-test.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/extents-test.c b/fs/ext4/extents-test.c
> index 6b53a3f39fcd..bd7795a82607 100644
> --- a/fs/ext4/extents-test.c
> +++ b/fs/ext4/extents-test.c
> @@ -37,6 +37,7 @@
>  
>  #include <kunit/test.h>
>  #include <kunit/static_stub.h>
> +#include <linux/fs_context.h>
>  #include <linux/gfp_types.h>
>  #include <linux/stddef.h>
>  
> @@ -130,14 +131,20 @@ static void ext_kill_sb(struct super_block *sb)
>  	generic_shutdown_super(sb);
>  }
>  
> -static int ext_set(struct super_block *sb, void *data)
> +static int ext_init_fs_context(struct fs_context *fc)
> +{
> +	return 0;
> +}
> +
> +static int ext_set(struct super_block *sb, struct fs_context *fc)
>  {
>  	return 0;
>  }
>  
>  static struct file_system_type ext_fs_type = {
> -	.name = "extents test",
> -	.kill_sb = ext_kill_sb,
> +	.name		 = "extents test",
> +	.init_fs_context = ext_init_fs_context,
> +	.kill_sb	 = ext_kill_sb,
>  };
>  
>  static void extents_kunit_exit(struct kunit *test)
> @@ -223,6 +230,7 @@ static int extents_kunit_init(struct kunit *test)
>  	struct ext4_inode_info *ei;
>  	struct inode *inode;
>  	struct super_block *sb;
> +	struct fs_context *fc;
>  	struct ext4_sb_info *sbi = NULL;
>  	struct kunit_ext_test_param *param =
>  		(struct kunit_ext_test_param *)(test->param_value);
> @@ -232,7 +240,13 @@ static int extents_kunit_init(struct kunit *test)
>  	if (sbi == NULL)
>  		return -ENOMEM;
>  
> -	sb = sget(&ext_fs_type, NULL, ext_set, 0, NULL);
> +	fc = fs_context_for_mount(&ext_fs_type, 0);
> +	if (IS_ERR(fc)) {
> +		kfree(sbi);
> +		return PTR_ERR(fc);
> +	}
> +	sb = sget_fc(fc, NULL, ext_set);
> +	put_fs_context(fc);
>  	if (IS_ERR(sb)) {
>  		kfree(sbi);
>  		return PTR_ERR(sb);
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH v2 2/4] ext4: convert mballoc KUnit test to sget_fc()

[Jan Kara]

On Fri 29-05-26 10:43:41, Christian Brauner wrote:
> Same treatment as the extents KUnit test. The mballoc test uses sget()
> as a thin "give me an initialized superblock" wrapper for a fake
> file_system_type. Move it onto sget_fc() so sget() can go away.
> 
> Add a no-op mbt_init_fs_context() so fs_context_for_mount() has
> something to call on the fake fs_type. mbt_set() now takes a struct
> fs_context * (still a no-op). mbt_ext4_alloc_super_block() allocates
> the fc, hands it to sget_fc() and drops the fc reference once the sb
> is published.
> 
> No functional change.
> 
> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext4/mballoc-test.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/mballoc-test.c b/fs/ext4/mballoc-test.c
> index 90ed505fa4b1..d90da44aadbd 100644
> --- a/fs/ext4/mballoc-test.c
> +++ b/fs/ext4/mballoc-test.c
> @@ -5,6 +5,7 @@
>  
>  #include <kunit/test.h>
>  #include <kunit/static_stub.h>
> +#include <linux/fs_context.h>
>  #include <linux/random.h>
>  
>  #include "ext4.h"
> @@ -63,8 +64,14 @@ static void mbt_kill_sb(struct super_block *sb)
>  	generic_shutdown_super(sb);
>  }
>  
> +static int mbt_init_fs_context(struct fs_context *fc)
> +{
> +	return 0;
> +}
> +
>  static struct file_system_type mbt_fs_type = {
>  	.name			= "mballoc test",
> +	.init_fs_context	= mbt_init_fs_context,
>  	.kill_sb		= mbt_kill_sb,
>  };
>  
> @@ -127,7 +134,7 @@ static void mbt_mb_release(struct super_block *sb)
>  	kfree(sb->s_bdev);
>  }
>  
> -static int mbt_set(struct super_block *sb, void *data)
> +static int mbt_set(struct super_block *sb, struct fs_context *fc)
>  {
>  	return 0;
>  }
> @@ -136,13 +143,19 @@ static struct super_block *mbt_ext4_alloc_super_block(void)
>  {
>  	struct mbt_ext4_super_block *fsb;
>  	struct super_block *sb;
> +	struct fs_context *fc;
>  	struct ext4_sb_info *sbi;
>  
>  	fsb = kzalloc_obj(*fsb);
>  	if (fsb == NULL)
>  		return NULL;
>  
> -	sb = sget(&mbt_fs_type, NULL, mbt_set, 0, NULL);
> +	fc = fs_context_for_mount(&mbt_fs_type, 0);
> +	if (IS_ERR(fc))
> +		goto out;
> +
> +	sb = sget_fc(fc, NULL, mbt_set);
> +	put_fs_context(fc);
>  	if (IS_ERR(sb))
>  		goto out;
>  
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH v2 4/4] fs: retire sget()

[Jan Kara]

On Fri 29-05-26 10:43:43, Christian Brauner wrote:
> sget() and sget_fc() have lived side by side as near-duplicate
> find-or-create-and-publish helpers for the legacy and fs_context mount
> APIs. The three remaining in-tree callers (CIFS plus the ext4 extents
> and mballoc KUnit tests) have all been moved to sget_fc(). Nothing
> calls sget() anymore.
> 
> Delete sget() from fs/super.c and the prototype in <linux/fs.h>.
> Update the two comments that referred to "sget()" or "sget{_fc}()" to
> just say "sget_fc()".
> 
> This removes ~60 lines of code that only existed to be kept in
> lockstep with sget_fc() on every superblock publish-path change.
> 
> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/btrfs/super.c   |  2 +-
>  fs/super.c         | 71 ++++--------------------------------------------------
>  include/linux/fs.h |  4 ---
>  3 files changed, 6 insertions(+), 71 deletions(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index b26aa9169e83..636154861d7c 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -2052,7 +2052,7 @@ static int btrfs_get_tree_subvol(struct fs_context *fc)
>  	 * then open_ctree will properly initialize the file system specific
>  	 * settings later.  btrfs_init_fs_info initializes the static elements
>  	 * of the fs_info (locks and such) to make cleanup easier if we find a
> -	 * superblock with our given fs_devices later on at sget() time.
> +	 * superblock with our given fs_devices later on at sget_fc() time.
>  	 */
>  	fs_info = kvzalloc_obj(struct btrfs_fs_info);
>  	if (!fs_info)
> diff --git a/fs/super.c b/fs/super.c
> index 378e81efe643..5fe8cea9f8fe 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -328,7 +328,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
>  	init_rwsem(&s->s_umount);
>  	lockdep_set_class(&s->s_umount, &type->s_umount_key);
>  	/*
> -	 * sget() can have s_umount recursion.
> +	 * sget_fc() can have s_umount recursion.
>  	 *
>  	 * When it cannot find a suitable sb, it allocates a new
>  	 * one (this one), and tries again to find a suitable old
> @@ -439,7 +439,7 @@ static void kill_super_notify(struct super_block *sb)
>  
>  	/*
>  	 * Remove it from @fs_supers so it isn't found by new
> -	 * sget{_fc}() walkers anymore. Any concurrent mounter still
> +	 * sget_fc() walkers anymore. Any concurrent mounter still
>  	 * managing to grab a temporary reference is guaranteed to
>  	 * already see SB_DYING and will wait until we notify them about
>  	 * SB_DEAD.
> @@ -517,7 +517,7 @@ EXPORT_SYMBOL(deactivate_super);
>   * @sb: superblock to acquire
>   *
>   * Acquire a temporary reference on a superblock and try to trade it for
> - * an active reference. This is used in sget{_fc}() to wait for a
> + * an active reference. This is used in sget_fc() to wait for a
>   * superblock to either become SB_BORN or for it to pass through
>   * sb->kill() and be marked as SB_DEAD.
>   *
> @@ -673,11 +673,11 @@ void generic_shutdown_super(struct super_block *sb)
>  	/*
>  	 * Broadcast to everyone that grabbed a temporary reference to this
>  	 * superblock before we removed it from @fs_supers that the superblock
> -	 * is dying. Every walker of @fs_supers outside of sget{_fc}() will now
> +	 * is dying. Every walker of @fs_supers outside of sget_fc() will now
>  	 * discard this superblock and treat it as dead.
>  	 *
>  	 * We leave the superblock on @fs_supers so it can be found by
> -	 * sget{_fc}() until we passed sb->kill_sb().
> +	 * sget_fc() until we passed sb->kill_sb().
>  	 */
>  	super_wake(sb, SB_DYING);
>  	super_unlock_excl(sb);
> @@ -808,67 +808,6 @@ struct super_block *sget_fc(struct fs_context *fc,
>  }
>  EXPORT_SYMBOL(sget_fc);
>  
> -/**
> - *	sget	-	find or create a superblock
> - *	@type:	  filesystem type superblock should belong to
> - *	@test:	  comparison callback
> - *	@set:	  setup callback
> - *	@flags:	  mount flags
> - *	@data:	  argument to each of them
> - */
> -struct super_block *sget(struct file_system_type *type,
> -			int (*test)(struct super_block *,void *),
> -			int (*set)(struct super_block *,void *),
> -			int flags,
> -			void *data)
> -{
> -	struct user_namespace *user_ns = current_user_ns();
> -	struct super_block *s = NULL;
> -	struct super_block *old;
> -	int err;
> -
> -retry:
> -	spin_lock(&sb_lock);
> -	if (test) {
> -		hlist_for_each_entry(old, &type->fs_supers, s_instances) {
> -			if (!test(old, data))
> -				continue;
> -			if (user_ns != old->s_user_ns) {
> -				spin_unlock(&sb_lock);
> -				destroy_unused_super(s);
> -				return ERR_PTR(-EBUSY);
> -			}
> -			if (!grab_super(old))
> -				goto retry;
> -			destroy_unused_super(s);
> -			return old;
> -		}
> -	}
> -	if (!s) {
> -		spin_unlock(&sb_lock);
> -		s = alloc_super(type, flags, user_ns);
> -		if (!s)
> -			return ERR_PTR(-ENOMEM);
> -		goto retry;
> -	}
> -
> -	err = set(s, data);
> -	if (err) {
> -		spin_unlock(&sb_lock);
> -		destroy_unused_super(s);
> -		return ERR_PTR(err);
> -	}
> -	s->s_type = type;
> -	strscpy(s->s_id, type->name, sizeof(s->s_id));
> -	list_add_tail(&s->s_list, &super_blocks);
> -	hlist_add_head(&s->s_instances, &type->fs_supers);
> -	spin_unlock(&sb_lock);
> -	get_filesystem(type);
> -	shrinker_register(s->s_shrink);
> -	return s;
> -}
> -EXPORT_SYMBOL(sget);
> -
>  void drop_super(struct super_block *sb)
>  {
>  	super_unlock_shared(sb);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 11559c513dfb..6dbe3218dc1e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2327,10 +2327,6 @@ void free_anon_bdev(dev_t);
>  struct super_block *sget_fc(struct fs_context *fc,
>  			    int (*test)(struct super_block *, struct fs_context *),
>  			    int (*set)(struct super_block *, struct fs_context *));
> -struct super_block *sget(struct file_system_type *type,
> -			int (*test)(struct super_block *,void *),
> -			int (*set)(struct super_block *,void *),
> -			int flags, void *data);
>  struct super_block *sget_dev(struct fs_context *fc, dev_t dev);
>  
>  /* Alas, no aliases. Too much hassle with bringing module.h everywhere */
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR