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Subject[PATCHv4 01/17] VFS: introduce helpers for the s_dirty flag
Date
From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch introduces 3 new VFS helpers: 'mark_sb_dirty()',
'mark_sb_clean()', and 'is_sb_dirty()'. The helpers simply
set 'sb->s_dirt' or test 'sb->s_dirt'. The plan is to make
every FS use these helpers instead of manipulating the
'sb->s_dirt' flag directly.

Ultimately, this change is a preparation for the periodic
superblock synchronization optimization which is about
preventing the "sync_supers" kernel thread from waking up
even if there is nothing to synchronize.

This patch also makes VFS use the new helpers.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Tigran A. Aivazian <tigran@aivazian.fsnet.co.uk>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Cc: linux-ext4@vger.kernel.org
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: reiserfs-devel@vger.kernel.org
Cc: Jan Kara <jack@suse.cz>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
---
fs/super.c | 4 ++--
fs/sync.c | 2 +-
include/linux/fs.h | 17 +++++++++++++++++
3 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/fs/super.c b/fs/super.c
index 69688b1..2b418fb 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -368,12 +368,12 @@ void sync_supers(void)
list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
if (list_empty(&sb->s_instances))
continue;
- if (sb->s_op->write_super && sb->s_dirt) {
+ if (sb->s_op->write_super && is_sb_dirty(sb)) {
sb->s_count++;
spin_unlock(&sb_lock);

down_read(&sb->s_umount);
- if (sb->s_root && sb->s_dirt)
+ if (sb->s_root && is_sb_dirty(sb))
sb->s_op->write_super(sb);
up_read(&sb->s_umount);

diff --git a/fs/sync.c b/fs/sync.c
index e8cbd41..782e466 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -144,7 +144,7 @@ int file_fsync(struct file *filp, struct dentry *dentry, int datasync)

/* sync the superblock to buffers */
sb = inode->i_sb;
- if (sb->s_dirt && sb->s_op->write_super)
+ if (is_sb_dirty(sb) && sb->s_op->write_super)
sb->s_op->write_super(sb);

/* .. finally sync the buffers to disk */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b336cb9..21fe2b3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1782,6 +1782,23 @@ extern int get_sb_pseudo(struct file_system_type *, char *,
struct vfsmount *mnt);
extern void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb);

+/*
+ * Note, VFS does not provide any serialization for the super block clean/dirty
+ * state changes, file-systems should take care of this.
+ */
+static inline void mark_sb_dirty(struct super_block *sb)
+{
+ sb->s_dirt = 1;
+}
+static inline void mark_sb_clean(struct super_block *sb)
+{
+ sb->s_dirt = 0;
+}
+static inline int is_sb_dirty(struct super_block *sb)
+{
+ return sb->s_dirt;
+}
+
/* Alas, no aliases. Too much hassle with bringing module.h everywhere */
#define fops_get(fops) \
(((fops) && try_module_get((fops)->owner) ? (fops) : NULL))
--
1.6.6.1


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