ext4: Clean up s_dirt handling

We don't need to set s_dirt in most of the ext4 code when journaling
is enabled.  In ext3/4 some of the summary statistics for # of free
inodes, blocks, and directories are calculated from the per-block
group statistics when the file system is mounted or unmounted.  As a
result the superblock doesn't have to be updated, either via the
journal or by setting s_dirt.  There are a few exceptions, most
notably when resizing the file system, where the superblock needs to
be modified --- and in that case it should be done as a journalled
operation if possible, and s_dirt set only in no-journal mode.

This patch will optimize out some unneeded disk writes when using ext4
with a journal.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

9 files changed, 36 insertions, 16 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 95b7594c76f9..bd30799a43ed 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -377,14 +377,11 @@ void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
         ext4_grpblk_t bit;
         unsigned int i;
         struct ext4_group_desc *desc;
-        struct ext4_super_block *es;
-        struct ext4_sb_info *sbi;
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
         int err = 0, ret, blk_free_count;
         ext4_grpblk_t blocks_freed;
         struct ext4_group_info *grp;
 
-        sbi = EXT4_SB(sb);
-        es = sbi->s_es;
         ext4_debug("Adding block(s) %llu-%llu\n", block, block + count - 1);
 
         ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
@@ -477,7 +474,6 @@ void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
         ret = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
         if (!err)
                 err = ret;
-        sb->s_dirt = 1;
 
 error_return:
         brelse(bitmap_bh);
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 19a4de57128a..8b56b53328eb 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1860,6 +1860,12 @@ static inline void ext4_unlock_group(struct super_block *sb,
         spin_unlock(ext4_group_lock_ptr(sb, group));
 }
 
+static inline void ext4_mark_super_dirty(struct super_block *sb)
+{
+        if (EXT4_SB(sb)->s_journal == NULL)
+                sb->s_dirt =1;
+}
+
 /*
  * Inodes and files operations
  */
diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index 53d2764d71ca..cfd27b38fa15 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -143,3 +143,19 @@ int __ext4_handle_dirty_metadata(const char *where, handle_t *handle,
         }
         return err;
 }
+
+int __ext4_handle_dirty_super(const char *where, handle_t *handle,
+                              struct super_block *sb)
+{
+        struct buffer_head *bh = EXT4_SB(sb)->s_sbh;
+        int err = 0;
+
+        if (ext4_handle_valid(handle)) {
+                err = jbd2_journal_dirty_metadata(handle, bh);
+                if (err)
+                        ext4_journal_abort_handle(where, __func__, bh,
+                                                  handle, err);
+        } else
+                sb->s_dirt = 1;
+        return err;
+}
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index dade0c024797..8ae8168900bf 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -141,6 +141,9 @@ int __ext4_journal_get_create_access(const char *where,
 int __ext4_handle_dirty_metadata(const char *where, handle_t *handle,
                                  struct inode *inode, struct buffer_head *bh);
 
+int __ext4_handle_dirty_super(const char *where, handle_t *handle,
+                              struct super_block *sb);
+
 #define ext4_journal_get_undo_access(handle, bh) \
         __ext4_journal_get_undo_access(__func__, (handle), (bh))
 #define ext4_journal_get_write_access(handle, bh) \
@@ -152,6 +155,8 @@ int __ext4_handle_dirty_metadata(const char *where, handle_t *handle,
         __ext4_journal_get_create_access(__func__, (handle), (bh))
 #define ext4_handle_dirty_metadata(handle, inode, bh) \
         __ext4_handle_dirty_metadata(__func__, (handle), (inode), (bh))
+#define ext4_handle_dirty_super(handle, sb) \
+        __ext4_handle_dirty_super(__func__, (handle), (sb))
 
 handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks);
 int __ext4_journal_stop(const char *where, handle_t *handle);
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 5313ae4cda2d..bd411c12d63d 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -123,7 +123,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
                 if (!IS_ERR(cp)) {
                         memcpy(sbi->s_es->s_last_mounted, cp,
                                sizeof(sbi->s_es->s_last_mounted));
-                        sb->s_dirt = 1;
+                        ext4_mark_super_dirty(sb);
                 }
         }
         return dquot_file_open(inode, filp);
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 25c4b3173fd9..ac377505ed57 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -279,7 +279,7 @@ out:
                 err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
                 if (!fatal)
                         fatal = err;
-                sb->s_dirt = 1;
+                ext4_mark_super_dirty(sb);
         } else
                 ext4_error(sb, "bit already cleared for inode %lu", ino);
 
@@ -965,7 +965,7 @@ got:
         percpu_counter_dec(&sbi->s_freeinodes_counter);
         if (S_ISDIR(mode))
                 percpu_counter_inc(&sbi->s_dirs_counter);
-        sb->s_dirt = 1;
+        ext4_mark_super_dirty(sb);
 
         if (sbi->s_log_groups_per_flex) {
                 flex_group = ext4_flex_group(sbi, group);
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 12b3bc026a68..d9d267181ddc 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2812,7 +2812,7 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
         err = ext4_handle_dirty_metadata(handle, NULL, gdp_bh);
 
 out_err:
-        sb->s_dirt = 1;
+        ext4_mark_super_dirty(sb);
         brelse(bitmap_bh);
         return err;
 }
@@ -4680,7 +4680,7 @@ do_more:
                 put_bh(bitmap_bh);
                 goto do_more;
         }
-        sb->s_dirt = 1;
+        ext4_mark_super_dirty(sb);
 error_return:
         if (freed)
                 dquot_free_block(inode, freed);
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 6df797eb9aeb..27527ae466ea 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -921,8 +921,7 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
                            &sbi->s_flex_groups[flex_group].free_inodes);
         }
 
-        ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
-        sb->s_dirt = 1;
+        ext4_handle_dirty_super(handle, sb);
 
 exit_journal:
         mutex_unlock(&sbi->s_resize_lock);
@@ -1045,13 +1044,12 @@ int ext4_group_extend(struct super_block *sb, struct ext4_super_block *es,
                 goto exit_put;
         }
         ext4_blocks_count_set(es, o_blocks_count + add);
-        ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
-        sb->s_dirt = 1;
         mutex_unlock(&EXT4_SB(sb)->s_resize_lock);
         ext4_debug("freeing blocks %llu through %llu\n", o_blocks_count,
                    o_blocks_count + add);
         /* We add the blocks to the bitmap and set the group need init bit */
         ext4_add_groupblocks(handle, sb, o_blocks_count, add);
+        ext4_handle_dirty_super(handle, sb);
         ext4_debug("freed blocks %llu through %llu\n", o_blocks_count,
                    o_blocks_count + add);
         if ((err = ext4_journal_stop(handle)))
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 04338009793a..a6f314249574 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -458,8 +458,7 @@ static void ext4_xattr_update_super_block(handle_t *handle,
 
         if (ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh) == 0) {
                 EXT4_SET_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_EXT_ATTR);
-                sb->s_dirt = 1;
-                ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
+                ext4_handle_dirty_super(handle, sb);
         }
 }