[PATCH 0/25 v2] fs: Convert all embedded bdis into separate ones

[PATCH 0/25 v2] fs: Convert all embedded bdis into separate ones

[Jan Kara]

Hello,

this is the second revision of the patch series which converts all embedded
occurences of struct backing_dev_info to use standalone dynamically allocated
structures. This makes bdi handling unified across all bdi users and generally
removes some boilerplate code from filesystems setting up their own bdi. It
also allows us to remove some code from generic bdi implementation.

The patches were only compile-tested for most filesystems (I've tested
mounting only for NFS & btrfs) so fs maintainers please have a look whether
the changes look sound to you.

This series is based on top of bdi fixes that were merged into linux-block
git tree into for-next branch. I have pushed out the result as a branch to

git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git bdi

Changes since v1:
* Added some acks
* Added further FUSE cleanup patch
* Added removal of unused argument to bdi_register()
* Fixed up some compilation failures spotted by 0-day testing

								Honza

[PATCH 04/25] fs: Provide infrastructure for dynamic BDIs in filesystems

[Jan Kara]

Provide helper functions for setting up dynamically allocated
backing_dev_info structures for filesystems and cleaning them up on
superblock destruction.

CC: linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
CC: linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
CC: Petr Vandrovec <petr-vPk2MGR0e28uaRcfnNAh7A@public.gmane.org>
CC: linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
CC: cluster-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
CC: osd-dev-yNzVSZO3znNg9hUCZPvPmw@public.gmane.org
CC: codalist-/uMB558Y47wP4a1z8dhFYw@public.gmane.org
CC: linux-afs-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
CC: ecryptfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
CC: linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
CC: ceph-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
CC: linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
CC: v9fs-developer-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
CC: lustre-devel-aLEFhgZF4x6X6Mz3xDxJMA@public.gmane.org
Signed-off-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/super.c                       | 49 ++++++++++++++++++++++++++++++++++++++++
 include/linux/backing-dev-defs.h |  2 +-
 include/linux/fs.h               |  6 +++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/fs/super.c b/fs/super.c
index b8b6a086c03b..0f51a437c269 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -446,6 +446,11 @@ void generic_shutdown_super(struct super_block *sb)
 	hlist_del_init(&sb->s_instances);
 	spin_unlock(&sb_lock);
 	up_write(&sb->s_umount);
+	if (sb->s_iflags & SB_I_DYNBDI) {
+		bdi_put(sb->s_bdi);
+		sb->s_bdi = &noop_backing_dev_info;
+		sb->s_iflags &= ~SB_I_DYNBDI;
+	}
 }
 
 EXPORT_SYMBOL(generic_shutdown_super);
@@ -1256,6 +1261,50 @@ mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
 }
 
 /*
+ * Setup private BDI for given superblock. It gets automatically cleaned up
+ * in generic_shutdown_super().
+ */
+int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
+{
+	struct backing_dev_info *bdi;
+	int err;
+	va_list args;
+
+	bdi = bdi_alloc(GFP_KERNEL);
+	if (!bdi)
+		return -ENOMEM;
+
+	bdi->name = sb->s_type->name;
+
+	va_start(args, fmt);
+	err = bdi_register_va(bdi, NULL, fmt, args);
+	va_end(args);
+	if (err) {
+		bdi_put(bdi);
+		return err;
+	}
+	WARN_ON(sb->s_bdi != &noop_backing_dev_info);
+	sb->s_bdi = bdi;
+	sb->s_iflags |= SB_I_DYNBDI;
+
+	return 0;
+}
+EXPORT_SYMBOL(super_setup_bdi_name);
+
+/*
+ * Setup private BDI for given superblock. I gets automatically cleaned up
+ * in generic_shutdown_super().
+ */
+int super_setup_bdi(struct super_block *sb)
+{
+	static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
+
+	return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
+				    atomic_long_inc_return(&bdi_seq));
+}
+EXPORT_SYMBOL(super_setup_bdi);
+
+/*
  * This is an internal function, please use sb_end_{write,pagefault,intwrite}
  * instead.
  */
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index e66d4722db8e..866c433e7d32 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -146,7 +146,7 @@ struct backing_dev_info {
 	congested_fn *congested_fn; /* Function pointer if device is md/dm */
 	void *congested_data;	/* Pointer to aux data for congested func */
 
-	char *name;
+	const char *name;
 
 	struct kref refcnt;	/* Reference counter for the structure */
 	unsigned int capabilities; /* Device capabilities */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7251f7bb45e8..98cf14ea78c0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1272,6 +1272,9 @@ struct mm_struct;
 /* sb->s_iflags to limit user namespace mounts */
 #define SB_I_USERNS_VISIBLE		0x00000010 /* fstype already mounted */
 
+/* Temporary flag until all filesystems are converted to dynamic bdis */
+#define SB_I_DYNBDI	0x00000100
+
 /* Possible states of 'frozen' field */
 enum {
 	SB_UNFROZEN = 0,		/* FS is unfrozen */
@@ -2121,6 +2124,9 @@ extern int vfs_ustat(dev_t, struct kstatfs *);
 extern int freeze_super(struct super_block *super);
 extern int thaw_super(struct super_block *super);
 extern bool our_mnt(struct vfsmount *mnt);
+extern __printf(2, 3)
+int super_setup_bdi_name(struct super_block *sb, char *fmt, ...);
+extern int super_setup_bdi(struct super_block *sb);
 
 extern int current_umask(void);
 
-- 
2.10.2

Re: [PATCH 04/25] fs: Provide infrastructure for dynamic BDIs in filesystems

[Christoph Hellwig]

> +	if (sb->s_iflags & SB_I_DYNBDI) {
> +		bdi_put(sb->s_bdi);
> +		sb->s_bdi = &noop_backing_dev_info;

At some point I'd really like to get rid of noop_backing_dev_info and
have a NULL here..

Otherwise this looks fine..

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH 19/25] nilfs2: Convert to properly refcounting bdi

[Jan Kara]

Similarly to set_bdev_super() NILFS2 just used block device reference to
bdi. Convert it to properly getting bdi reference. The reference will
get automatically dropped on superblock destruction.

CC: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
CC: linux-nilfs@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/nilfs2/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index e1872f36147f..feb796a38b8d 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1068,7 +1068,8 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_time_gran = 1;
 	sb->s_max_links = NILFS_LINK_MAX;
 
-	sb->s_bdi = bdev_get_queue(sb->s_bdev)->backing_dev_info;
+	sb->s_bdi = bdi_get(sb->s_bdev->bd_bdi);
+	sb->s_iflags |= SB_I_DYNBDI;
 
 	err = load_nilfs(nilfs, sb);
 	if (err)
-- 
2.10.2

Re: [PATCH 19/25] nilfs2: Convert to properly refcounting bdi

[Christoph Hellwig]

On Wed, Mar 29, 2017 at 12:56:17PM +0200, Jan Kara wrote:
> Similarly to set_bdev_super() NILFS2 just used block device reference to
> bdi. Convert it to properly getting bdi reference. The reference will
> get automatically dropped on superblock destruction.

I really wish we could get rid of this open coding in block based
file systems..

Otherwise looks fine:

Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
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Re: [PATCH 19/25] nilfs2: Convert to properly refcounting bdi

[Jan Kara]

On Wed 12-04-17 01:17:46, Christoph Hellwig wrote:
> On Wed, Mar 29, 2017 at 12:56:17PM +0200, Jan Kara wrote:
> > Similarly to set_bdev_super() NILFS2 just used block device reference to
> > bdi. Convert it to properly getting bdi reference. The reference will
> > get automatically dropped on superblock destruction.
> 
> I really wish we could get rid of this open coding in block based
> file systems..

Well, nilfs has it because it has its own ->mount implementation (and
similarly gfs2). If someone has idea how common code out of those could be
factored out, bdi handling could be part of that...

> Otherwise looks fine:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR