[PATCH 0/25 v3] fs: Convert all embedded bdis into separate ones

[PATCH 0/25 v3] fs: Convert all embedded bdis into separate ones

[Jan Kara]

Hello,

this is the third 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

Since all patches got reviewed by Christoph, can you please pick them up Jens?
Thanks!

Changes since v2:
* Added Reviewed-by tags from Christoph

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@lists.infradead.org
CC: linux-nfs@vger.kernel.org
CC: Petr Vandrovec <petr@vandrovec.name>
CC: linux-nilfs@vger.kernel.org
CC: cluster-devel@redhat.com
CC: osd-dev@open-osd.org
CC: codalist@coda.cs.cmu.edu
CC: linux-afs@lists.infradead.org
CC: ecryptfs@vger.kernel.org
CC: linux-cifs@vger.kernel.org
CC: ceph-devel@vger.kernel.org
CC: linux-btrfs@vger.kernel.org
CC: v9fs-developer@lists.sourceforge.net
CC: lustre-devel@lists.lustre.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 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);
 
-- 
2.12.0

[PATCH 10/25] cifs: Convert to separately allocated bdi

[Jan Kara]

Allocate struct backing_dev_info separately instead of embedding it
inside superblock. This unifies handling of bdi among users.

CC: Steve French <sfrench@samba.org>
CC: linux-cifs@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/cifs/cifs_fs_sb.h |  1 -
 fs/cifs/cifsfs.c     |  7 ++++++-
 fs/cifs/connect.c    | 10 ----------
 3 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 07ed81cf1552..cbd216b57239 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -68,7 +68,6 @@ struct cifs_sb_info {
 	umode_t	mnt_dir_mode;
 	unsigned int mnt_cifs_flags;
 	char   *mountdata; /* options received at mount time or via DFS refs */
-	struct backing_dev_info bdi;
 	struct delayed_work prune_tlinks;
 	struct rcu_head rcu;
 	char *prepath;
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 15e1db8738ae..502eab6bdbc4 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -138,7 +138,12 @@ cifs_read_super(struct super_block *sb)
 	sb->s_magic = CIFS_MAGIC_NUMBER;
 	sb->s_op = &cifs_super_ops;
 	sb->s_xattr = cifs_xattr_handlers;
-	sb->s_bdi = &cifs_sb->bdi;
+	rc = super_setup_bdi(sb);
+	if (rc)
+		goto out_no_root;
+	/* tune readahead according to rsize */
+	sb->s_bdi->ra_pages = cifs_sb->rsize / PAGE_SIZE;
+
 	sb->s_blocksize = CIFS_MAX_MSGSIZE;
 	sb->s_blocksize_bits = 14;	/* default 2**14 = CIFS_MAX_MSGSIZE */
 	inode = cifs_root_iget(sb);
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 9ae695ae3ed7..7f50c8949401 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3683,10 +3683,6 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 	int referral_walks_count = 0;
 #endif
 
-	rc = bdi_setup_and_register(&cifs_sb->bdi, "cifs");
-	if (rc)
-		return rc;
-
 #ifdef CONFIG_CIFS_DFS_UPCALL
 try_mount_again:
 	/* cleanup activities if we're chasing a referral */
@@ -3714,7 +3710,6 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 	server = cifs_get_tcp_session(volume_info);
 	if (IS_ERR(server)) {
 		rc = PTR_ERR(server);
-		bdi_destroy(&cifs_sb->bdi);
 		goto out;
 	}
 	if ((volume_info->max_credits < 20) ||
@@ -3768,9 +3763,6 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 	cifs_sb->wsize = server->ops->negotiate_wsize(tcon, volume_info);
 	cifs_sb->rsize = server->ops->negotiate_rsize(tcon, volume_info);
 
-	/* tune readahead according to rsize */
-	cifs_sb->bdi.ra_pages = cifs_sb->rsize / PAGE_SIZE;
-
 remote_path_check:
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	/*
@@ -3887,7 +3879,6 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 			cifs_put_smb_ses(ses);
 		else
 			cifs_put_tcp_session(server, 0);
-		bdi_destroy(&cifs_sb->bdi);
 	}
 
 out:
@@ -4090,7 +4081,6 @@ cifs_umount(struct cifs_sb_info *cifs_sb)
 	}
 	spin_unlock(&cifs_sb->tlink_tree_lock);
 
-	bdi_destroy(&cifs_sb->bdi);
 	kfree(cifs_sb->mountdata);
 	kfree(cifs_sb->prepath);
 	call_rcu(&cifs_sb->rcu, delayed_free);
-- 
2.12.0

Re: [PATCH 0/25 v3] fs: Convert all embedded bdis into separate ones

[Jens Axboe]

On Wed, Apr 12 2017, Jan Kara wrote:
> Hello,
> 
> this is the third 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
> 
> Since all patches got reviewed by Christoph, can you please pick them up Jens?
> Thanks!

Yep, picked up for 4.12. Thanks Jan!

-- 
Jens Axboe