hfsplus: get rid of write_super

This patch makes hfsplus stop using the VFS '->write_super()' method along with
the 's_dirt' superblock flag, because they are on their way out.

The whole "superblock write-out" VFS infrastructure is served by the
'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds and
writes out all dirty superblocks using the '->write_super()' call-back.  But the
problem with this thread is that it wastes power by waking up the system every
5 seconds, even if there are no diry superblocks, or there are no client
file-systems which would need this (e.g., btrfs does not use
'->write_super()'). So we want to kill it completely and thus, we need to make
file-systems to stop using the '->write_super()' VFS service, and then remove
it together with the kernel thread.

Tested using fsstress from the LTP project.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

5 files changed, 43 insertions, 16 deletions

diff --git a/fs/hfsplus/bitmap.c b/fs/hfsplus/bitmap.c
index 1cad80c789cb..4cfbe2edd296 100644
--- a/fs/hfsplus/bitmap.c
+++ b/fs/hfsplus/bitmap.c
@@ -153,7 +153,7 @@ done:
         kunmap(page);
         *max = offset + (curr - pptr) * 32 + i - start;
         sbi->free_blocks -= *max;
-        sb->s_dirt = 1;
+        hfsplus_mark_mdb_dirty(sb);
         dprint(DBG_BITMAP, "-> %u,%u\n", start, *max);
 out:
         mutex_unlock(&sbi->alloc_mutex);
@@ -228,7 +228,7 @@ out:
         set_page_dirty(page);
         kunmap(page);
         sbi->free_blocks += len;
-        sb->s_dirt = 1;
+        hfsplus_mark_mdb_dirty(sb);
         mutex_unlock(&sbi->alloc_mutex);
 
         return 0;
diff --git a/fs/hfsplus/dir.c b/fs/hfsplus/dir.c
index 378ea0c43f19..6b9f921ef2fa 100644
--- a/fs/hfsplus/dir.c
+++ b/fs/hfsplus/dir.c
@@ -316,7 +316,7 @@ static int hfsplus_link(struct dentry *src_dentry, struct inode *dst_dir,
         inode->i_ctime = CURRENT_TIME_SEC;
         mark_inode_dirty(inode);
         sbi->file_count++;
-        dst_dir->i_sb->s_dirt = 1;
+        hfsplus_mark_mdb_dirty(dst_dir->i_sb);
 out:
         mutex_unlock(&sbi->vh_mutex);
         return res;
diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
index 66a9365041be..558dbb463a4e 100644
--- a/fs/hfsplus/hfsplus_fs.h
+++ b/fs/hfsplus/hfsplus_fs.h
@@ -153,8 +153,11 @@ struct hfsplus_sb_info {
         gid_t gid;
 
         int part, session;
-
         unsigned long flags;
+
+        int work_queued;               /* non-zero delayed work is queued */
+        struct delayed_work sync_work; /* FS sync delayed work */
+        spinlock_t work_lock;          /* protects sync_work and work_queued */
 };
 
 #define HFSPLUS_SB_WRITEBACKUP  0
@@ -428,6 +431,7 @@ int hfsplus_show_options(struct seq_file *, struct dentry *);
 
 /* super.c */
 struct inode *hfsplus_iget(struct super_block *, unsigned long);
+void hfsplus_mark_mdb_dirty(struct super_block *sb);
 
 /* tables.c */
 extern u16 hfsplus_case_fold_table[];
diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
index 7009265b746f..3d8b4a675ba0 100644
--- a/fs/hfsplus/inode.c
+++ b/fs/hfsplus/inode.c
@@ -431,7 +431,7 @@ struct inode *hfsplus_new_inode(struct super_block *sb, umode_t mode)
                 sbi->file_count++;
         insert_inode_hash(inode);
         mark_inode_dirty(inode);
-        sb->s_dirt = 1;
+        hfsplus_mark_mdb_dirty(sb);
 
         return inode;
 }
@@ -442,7 +442,7 @@ void hfsplus_delete_inode(struct inode *inode)
 
         if (S_ISDIR(inode->i_mode)) {
                 HFSPLUS_SB(sb)->folder_count--;
-                sb->s_dirt = 1;
+                hfsplus_mark_mdb_dirty(sb);
                 return;
         }
         HFSPLUS_SB(sb)->file_count--;
@@ -455,7 +455,7 @@ void hfsplus_delete_inode(struct inode *inode)
                 inode->i_size = 0;
                 hfsplus_file_truncate(inode);
         }
-        sb->s_dirt = 1;
+        hfsplus_mark_mdb_dirty(sb);
 }
 
 void hfsplus_inode_read_fork(struct inode *inode, struct hfsplus_fork_raw *fork)
diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index f4f3d5463061..473332098013 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -124,7 +124,7 @@ static int hfsplus_system_write_inode(struct inode *inode)
 
         if (fork->total_size != cpu_to_be64(inode->i_size)) {
                 set_bit(HFSPLUS_SB_WRITEBACKUP, &sbi->flags);
-                inode->i_sb->s_dirt = 1;
+                hfsplus_mark_mdb_dirty(inode->i_sb);
         }
         hfsplus_inode_write_fork(inode, fork);
         if (tree)
@@ -173,8 +173,6 @@ static int hfsplus_sync_fs(struct super_block *sb, int wait)
 
         dprint(DBG_SUPER, "hfsplus_sync_fs\n");
 
-        sb->s_dirt = 0;
-
         /*
          * Explicitly write out the special metadata inodes.
          *
@@ -226,12 +224,34 @@ out:
         return error;
 }
 
-static void hfsplus_write_super(struct super_block *sb)
+static void delayed_sync_fs(struct work_struct *work)
 {
-        if (!(sb->s_flags & MS_RDONLY))
-                hfsplus_sync_fs(sb, 1);
-        else
-                sb->s_dirt = 0;
+        struct hfsplus_sb_info *sbi;
+
+        sbi = container_of(work, struct hfsplus_sb_info, sync_work.work);
+
+        spin_lock(&sbi->work_lock);
+        sbi->work_queued = 0;
+        spin_unlock(&sbi->work_lock);
+
+        hfsplus_sync_fs(sbi->alloc_file->i_sb, 1);
+}
+
+void hfsplus_mark_mdb_dirty(struct super_block *sb)
+{
+        struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
+        unsigned long delay;
+
+        if (sb->s_flags & MS_RDONLY)
+                return;
+
+        spin_lock(&sbi->work_lock);
+        if (!sbi->work_queued) {
+                delay = msecs_to_jiffies(dirty_writeback_interval * 10);
+                queue_delayed_work(system_long_wq, &sbi->sync_work, delay);
+                sbi->work_queued = 1;
+        }
+        spin_unlock(&sbi->work_lock);
 }
 
 static void hfsplus_put_super(struct super_block *sb)
@@ -240,6 +260,8 @@ static void hfsplus_put_super(struct super_block *sb)
 
         dprint(DBG_SUPER, "hfsplus_put_super\n");
 
+        cancel_delayed_work_sync(&sbi->sync_work);
+
         if (!(sb->s_flags & MS_RDONLY) && sbi->s_vhdr) {
                 struct hfsplus_vh *vhdr = sbi->s_vhdr;
 
@@ -325,7 +347,6 @@ static const struct super_operations hfsplus_sops = {
         .write_inode    = hfsplus_write_inode,
         .evict_inode    = hfsplus_evict_inode,
         .put_super      = hfsplus_put_super,
-        .write_super    = hfsplus_write_super,
         .sync_fs        = hfsplus_sync_fs,
         .statfs         = hfsplus_statfs,
         .remount_fs     = hfsplus_remount,
@@ -352,6 +373,8 @@ static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
         sb->s_fs_info = sbi;
         mutex_init(&sbi->alloc_mutex);
         mutex_init(&sbi->vh_mutex);
+        spin_lock_init(&sbi->work_lock);
+        INIT_DELAYED_WORK(&sbi->sync_work, delayed_sync_fs);
         hfsplus_fill_defaults(sbi);
 
         err = -EINVAL;