fs/ufs: get rid of write_super

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

The way we implement this is that we schedule a delay job instead relying on
's_dirt' and '->write_super()'.

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, 42 insertions, 16 deletions

diff --git a/fs/ufs/balloc.c b/fs/ufs/balloc.c
index 42694e11c23d..1b3e410bf334 100644
--- a/fs/ufs/balloc.c
+++ b/fs/ufs/balloc.c
@@ -116,7 +116,7 @@ void ufs_free_fragments(struct inode *inode, u64 fragment, unsigned count)
         ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
         if (sb->s_flags & MS_SYNCHRONOUS)
                 ubh_sync_block(UCPI_UBH(ucpi));
-        sb->s_dirt = 1;
+        ufs_mark_sb_dirty(sb);
         
         unlock_super (sb);
         UFSD("EXIT\n");
@@ -214,7 +214,7 @@ do_more:
                 goto do_more;
         }
 
-        sb->s_dirt = 1;
+        ufs_mark_sb_dirty(sb);
         unlock_super (sb);
         UFSD("EXIT\n");
         return;
@@ -557,7 +557,7 @@ static u64 ufs_add_fragments(struct inode *inode, u64 fragment,
         ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
         if (sb->s_flags & MS_SYNCHRONOUS)
                 ubh_sync_block(UCPI_UBH(ucpi));
-        sb->s_dirt = 1;
+        ufs_mark_sb_dirty(sb);
 
         UFSD("EXIT, fragment %llu\n", (unsigned long long)fragment);
         
@@ -677,7 +677,7 @@ succed:
         ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
         if (sb->s_flags & MS_SYNCHRONOUS)
                 ubh_sync_block(UCPI_UBH(ucpi));
-        sb->s_dirt = 1;
+        ufs_mark_sb_dirty(sb);
 
         result += cgno * uspi->s_fpg;
         UFSD("EXIT3, result %llu\n", (unsigned long long)result);
diff --git a/fs/ufs/ialloc.c b/fs/ufs/ialloc.c
index 4ec5c1085a87..e84cbe21b986 100644
--- a/fs/ufs/ialloc.c
+++ b/fs/ufs/ialloc.c
@@ -116,7 +116,7 @@ void ufs_free_inode (struct inode * inode)
         if (sb->s_flags & MS_SYNCHRONOUS)
                 ubh_sync_block(UCPI_UBH(ucpi));
         
-        sb->s_dirt = 1;
+        ufs_mark_sb_dirty(sb);
         unlock_super (sb);
         UFSD("EXIT\n");
 }
@@ -288,7 +288,7 @@ cg_found:
         ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
         if (sb->s_flags & MS_SYNCHRONOUS)
                 ubh_sync_block(UCPI_UBH(ucpi));
-        sb->s_dirt = 1;
+        ufs_mark_sb_dirty(sb);
 
         inode->i_ino = cg * uspi->s_ipg + bit;
         inode_init_owner(inode, dir, mode);
diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index ad56c6dffc64..444927e5706b 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -302,7 +302,7 @@ void ufs_error (struct super_block * sb, const char * function,
         if (!(sb->s_flags & MS_RDONLY)) {
                 usb1->fs_clean = UFS_FSBAD;
                 ubh_mark_buffer_dirty(USPI_UBH(uspi));
-                sb->s_dirt = 1;
+                ufs_mark_sb_dirty(sb);
                 sb->s_flags |= MS_RDONLY;
         }
         va_start (args, fmt);
@@ -334,7 +334,7 @@ void ufs_panic (struct super_block * sb, const char * function,
         if (!(sb->s_flags & MS_RDONLY)) {
                 usb1->fs_clean = UFS_FSBAD;
                 ubh_mark_buffer_dirty(USPI_UBH(uspi));
-                sb->s_dirt = 1;
+                ufs_mark_sb_dirty(sb);
         }
         va_start (args, fmt);
         vsnprintf (error_buf, sizeof(error_buf), fmt, args);
@@ -715,7 +715,6 @@ static int ufs_sync_fs(struct super_block *sb, int wait)
                 ufs_set_fs_state(sb, usb1, usb3,
                                 UFS_FSOK - fs32_to_cpu(sb, usb1->fs_time));
         ufs_put_cstotal(sb);
-        sb->s_dirt = 0;
 
         UFSD("EXIT\n");
         unlock_super(sb);
@@ -724,12 +723,31 @@ static int ufs_sync_fs(struct super_block *sb, int wait)
         return 0;
 }
 
-static void ufs_write_super(struct super_block *sb)
+static void delayed_sync_fs(struct work_struct *work)
 {
-        if (!(sb->s_flags & MS_RDONLY))
-                ufs_sync_fs(sb, 1);
-        else
-                sb->s_dirt = 0;
+        struct ufs_sb_info *sbi;
+
+        sbi = container_of(work, struct ufs_sb_info, sync_work.work);
+
+        spin_lock(&sbi->work_lock);
+        sbi->work_queued = 0;
+        spin_unlock(&sbi->work_lock);
+
+        ufs_sync_fs(sbi->sb, 1);
+}
+
+void ufs_mark_sb_dirty(struct super_block *sb)
+{
+        struct ufs_sb_info *sbi = UFS_SB(sb);
+        unsigned long delay;
+
+        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 ufs_put_super(struct super_block *sb)
@@ -740,6 +758,7 @@ static void ufs_put_super(struct super_block *sb)
 
         if (!(sb->s_flags & MS_RDONLY))
                 ufs_put_super_internal(sb);
+        cancel_delayed_work_sync(&sbi->sync_work);
 
         ubh_brelse_uspi (sbi->s_uspi);
         kfree (sbi->s_uspi);
@@ -774,6 +793,7 @@ static int ufs_fill_super(struct super_block *sb, void *data, int silent)
         if (!sbi)
                 goto failed_nomem;
         sb->s_fs_info = sbi;
+        sbi->sb = sb;
 
         UFSD("flag %u\n", (int)(sb->s_flags & MS_RDONLY));
         
@@ -785,6 +805,8 @@ static int ufs_fill_super(struct super_block *sb, void *data, int silent)
         }
 #endif
         mutex_init(&sbi->mutex);
+        spin_lock_init(&sbi->work_lock);
+        INIT_DELAYED_WORK(&sbi->sync_work, delayed_sync_fs);
         /*
          * Set default mount options
          * Parse mount options
@@ -1304,7 +1326,6 @@ static int ufs_remount (struct super_block *sb, int *mount_flags, char *data)
                         ufs_set_fs_state(sb, usb1, usb3,
                                 UFS_FSOK - fs32_to_cpu(sb, usb1->fs_time));
                 ubh_mark_buffer_dirty (USPI_UBH(uspi));
-                sb->s_dirt = 0;
                 sb->s_flags |= MS_RDONLY;
         } else {
         /*
@@ -1454,7 +1475,6 @@ static const struct super_operations ufs_super_ops = {
         .write_inode    = ufs_write_inode,
         .evict_inode    = ufs_evict_inode,
         .put_super      = ufs_put_super,
-        .write_super    = ufs_write_super,
         .sync_fs        = ufs_sync_fs,
         .statfs         = ufs_statfs,
         .remount_fs     = ufs_remount,
diff --git a/fs/ufs/ufs.h b/fs/ufs/ufs.h
index 528750b7e701..343e6fc571e5 100644
--- a/fs/ufs/ufs.h
+++ b/fs/ufs/ufs.h
@@ -20,6 +20,10 @@ struct ufs_sb_info {
         unsigned s_mount_opt;
         struct mutex mutex;
         struct task_struct *mutex_owner;
+        struct super_block *sb;
+        int work_queued; /* non-zero if the delayed work is queued */
+        struct delayed_work sync_work; /* FS sync delayed work */
+        spinlock_t work_lock; /* protects sync_work and work_queued */
 };
 
 struct ufs_inode_info {
@@ -123,6 +127,7 @@ extern __printf(3, 4)
 void ufs_error(struct super_block *, const char *, const char *, ...);
 extern __printf(3, 4)
 void ufs_panic(struct super_block *, const char *, const char *, ...);
+void ufs_mark_sb_dirty(struct super_block *sb);
 
 /* symlink.c */
 extern const struct inode_operations ufs_fast_symlink_inode_operations;
diff --git a/fs/ufs/ufs_fs.h b/fs/ufs/ufs_fs.h
index 8aba544f9fad..0cbd5d340b67 100644
--- a/fs/ufs/ufs_fs.h
+++ b/fs/ufs/ufs_fs.h
@@ -34,6 +34,7 @@
 #include <linux/kernel.h>
 #include <linux/stat.h>
 #include <linux/fs.h>
+#include <linux/workqueue.h>
 
 #include <asm/div64.h>
 typedef __u64 __bitwise __fs64;