fs: Provide infrastructure for dynamic BDIs in filesystems

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>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/fs/super.c b/fs/super.c
index b8b6a086c03b9a5478dc6a67e0b5054127032f47..0f51a437c269a7517389154db5d0e81d93fa44da 100644 (file)
--- 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);
@@ -1255,6 +1260,50 @@ out:
        return ERR_PTR(error);
 }
 
+/*
+ * 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 e66d4722db8e4a95754e46a905e7bcf2cfa87ca3..866c433e7d3220b29170ed98ccd1b70803a43964 100644 (file)
--- 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 7251f7bb45e8b80b44f28c2051c5bef8e947e6bb..98cf14ea78c0e86c21ce3ac7a6a914643d8b06a7 100644 (file)
--- 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);