linux-ext4 - [PATCH v2 08/11] ext4: simplify journal handling in setup_new_group

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Date:	Tue, 19 Jul 2011 12:02:14 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	linux-ext4@...r.kernel.org
Cc:	adilger@...ger.ca, amir73il@...il.com, tm@....ma,
	Yongqiang Yang <xiaoqiangnk@...il.com>
Subject: [PATCH v2 08/11] ext4: simplify journal handling in setup_new_group_blocks()

This patch simplifies journal handling in setup_new_group_blocks().

In previous code, block bitmap is modified everywhere in
setup_new_group_blocks(), ext4_get_write_access() in
extend_or_restart_transaction() is used to guarantee that the block bitmap
stays in the new handle, this makes things complicated.

In this patch the modifications on the block bitmap are batched and done
by ext4_set_bits() after reqesting a handle from extend_or_restart_transaction()
with enough credits.  So ext4_get_write_access() can be removed from
extend_or_restart_transaction().

Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
---
 fs/ext4/resize.c |   39 ++++++++++++++++++++-------------------
 1 files changed, 20 insertions(+), 19 deletions(-)

 v1->v2:
    add commit log explainning it is safe to remove
    ext4_get_write_access() from extend_or_restart_transaction().

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 178fb2f..5b423f8 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -161,8 +161,7 @@ static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,
  * If that fails, restart the transaction & regain write access for the
  * buffer head which is used for block_bitmap modifications.
  */
-static int extend_or_restart_transaction(handle_t *handle, int thresh,
-					 struct buffer_head *bh)
+static int extend_or_restart_transaction(handle_t *handle, int thresh)
 {
 	int err;
 
@@ -173,9 +172,8 @@ static int extend_or_restart_transaction(handle_t *handle, int thresh,
 	if (err < 0)
 		return err;
 	if (err) {
-		if ((err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA)))
-			return err;
-		if ((err = ext4_journal_get_write_access(handle, bh)))
+		err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA);
+		if (err)
 			return err;
 	}
 
@@ -212,29 +210,24 @@ static int setup_new_group_blocks(struct super_block *sb,
 
 	BUG_ON(input->group != sbi->s_groups_count);
 
-	if (IS_ERR(bh = bclean(handle, sb, input->block_bitmap))) {
-		err = PTR_ERR(bh);
-		goto exit_journal;
-	}
-
 	/* Copy all of the GDT blocks into the backup in this group */
 	for (i = 0, bit = 1, block = start + 1;
 	     i < gdblocks; i++, block++, bit++) {
 		struct buffer_head *gdb;
 
 		ext4_debug("update backup group %#04llx (+%d)\n", block, bit);
-
-		if ((err = extend_or_restart_transaction(handle, 1, bh)))
-			goto exit_bh;
+		err = extend_or_restart_transaction(handle, 1);
+		if (err)
+			goto exit_journal;
 
 		gdb = sb_getblk(sb, block);
 		if (!gdb) {
 			err = -EIO;
-			goto exit_bh;
+			goto exit_journal;
 		}
 		if ((err = ext4_journal_get_write_access(handle, gdb))) {
 			brelse(gdb);
-			goto exit_bh;
+			goto exit_journal;
 		}
 		lock_buffer(gdb);
 		memcpy(gdb->b_data, sbi->s_group_desc[i]->b_data, gdb->b_size);
@@ -243,7 +236,7 @@ static int setup_new_group_blocks(struct super_block *sb,
 		err = ext4_handle_dirty_metadata(handle, NULL, gdb);
 		if (unlikely(err)) {
 			brelse(gdb);
-			goto exit_bh;
+			goto exit_journal;
 		}
 		brelse(gdb);
 	}
@@ -254,7 +247,17 @@ static int setup_new_group_blocks(struct super_block *sb,
 	err = sb_issue_zeroout(sb, gdblocks + start + 1, reserved_gdb,
 			       GFP_NOFS);
 	if (err)
-		goto exit_bh;
+		goto exit_journal;
+
+	err = extend_or_restart_transaction(handle, 2);
+	if (err)
+		goto exit_journal;
+
+	bh = bclean(handle, sb, input->block_bitmap);
+	if (IS_ERR(bh)) {
+		err = PTR_ERR(bh);
+		goto exit_journal;
+	}
 
 	if (ext4_bg_has_super(sb, input->group)) {
 		ext4_debug("mark backup group tables %#04llx (+0)\n", start);
@@ -278,8 +281,6 @@ static int setup_new_group_blocks(struct super_block *sb,
 	ext4_set_bits(bh->b_data, input->inode_table - start,
 		      sbi->s_itb_per_group);
 
-	if ((err = extend_or_restart_transaction(handle, 2, bh)))
-		goto exit_bh;
 
 	ext4_mark_bitmap_end(input->blocks_count, sb->s_blocksize * 8,
 			     bh->b_data);
-- 
1.7.5.1

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