Re: [PATCH -v2] ext4: Use inode preallocation with -o noextents

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

On Wed, Jun 04, 2008 at 11:22:20PM -0400, Theodore Tso wrote:
> when I moved this patch to the beginning of the unstable patch queue,
> it didn't apply.  When I tried to look at it, my head started
> spinning.  The patch applied to the wrong function, apparently,
> because there is so much code duplication "patch" got confused.  I
> can't blame it, though, because *I* got confused.  
> 
> fs/ext4/balloc.c is a complete disaster right now.  We have:
> 
> ext4_new_blocks_old()
> ext4_new_meta_block()
> ext4_new_meta_blocks()
> ext4_new_blocks()
> 
> ... and without any comments, it is extremely impenetrable.  Someone
> needs to document what the heck all of the various functions have to
> do with each other, when they get used (i.e., with which mount options). 
> 
> Why aren't we factoring out the last three into a single function?  

Something like below ? . I will send a final patch once I get the
patchqueu updated. I am not able to reach repo.or.cz currently.

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index bd18ceb..abbc500 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1656,7 +1656,7 @@ int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 }
 
 /**
- * ext4_new_blocks_old() -- core block(s) allocation function
+ * ext4_orlov_new_blocks() -- core block(s) allocation function
  * @handle:		handle to this transaction
  * @inode:		file inode
  * @goal:		given target block(filesystem wide)
@@ -1669,7 +1669,7 @@ int ext4_should_retry_alloc(struct super_block *sb, int *retries)
  * any specific goal block.
  *
  */
-ext4_fsblk_t ext4_new_blocks_old(handle_t *handle, struct inode *inode,
+ext4_fsblk_t ext4_orlov_new_blocks(handle_t *handle, struct inode *inode,
 			ext4_fsblk_t goal, unsigned long *count, int *errp)
 {
 	struct buffer_head *bitmap_bh = NULL;
@@ -1942,88 +1942,68 @@ ext4_fsblk_t ext4_new_blocks_old(handle_t *handle, struct inode *inode,
 	return 0;
 }
 
-ext4_fsblk_t ext4_new_meta_block(handle_t *handle, struct inode *inode,
-		ext4_fsblk_t goal, int *errp)
+static ext4_fsblk_t do_blk_alloc(handle_t *handle, struct inode *inode,
+				ext4_lblk_t iblock, ext4_fsblk_t goal,
+				unsigned long *count, int *errp, int meta)
 {
 	struct ext4_allocation_request ar;
 	ext4_fsblk_t ret;
 
 	if (!test_opt(inode->i_sb, MBALLOC)) {
-		unsigned long count = 1;
-		ret = ext4_new_blocks_old(handle, inode, goal, &count, errp);
+		ret = ext4_orlov_new_blocks(handle, inode, goal, count, errp);
 		return ret;
 	}
 
 	memset(&ar, 0, sizeof(ar));
+	/* Fill with neighbour allocated blocks */
+	ar.lleft  = 0;
+	ar.pleft  = 0;
+	ar.lright = 0;
+	ar.pright = 0;
+
 	ar.inode = inode;
 	ar.goal = goal;
-	ar.len = 1;
+	ar.len = *count;
+	ar.logical = iblock;
+	if (S_ISREG(inode->i_mode) && !meta)
+		ar.flags = EXT4_MB_HINT_DATA;
+	else
+		/* disable in-core preallocation for non-regular files */
+		ar.flags = 0;
 	ret = ext4_mb_new_blocks(handle, &ar, errp);
+	*count = ar.len;
 	/*
 	 * Account for the allocated meta blocks
 	 */
-	if (!(*errp)) {
+	if (!(*errp) && meta) {
 		spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 		EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 	}
-
 	return ret;
 }
+
+
+ext4_fsblk_t ext4_new_meta_block(handle_t *handle, struct inode *inode,
+		ext4_fsblk_t goal, int *errp)
+{
+	unsigned long count = 1;
+	return do_blk_alloc(handle, inode, 0, goal, &count, errp, 1);
+}
+
 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 		ext4_fsblk_t goal, unsigned long *count, int *errp)
 {
-	struct ext4_allocation_request ar;
-	ext4_fsblk_t ret;
-
-	if (!test_opt(inode->i_sb, MBALLOC)) {
-		ret = ext4_new_blocks_old(handle, inode, goal, count, errp);
-		return ret;
-	}
-
-	memset(&ar, 0, sizeof(ar));
-	ar.inode = inode;
-	ar.goal = goal;
-	ar.len = *count;
-	ret = ext4_mb_new_blocks(handle, &ar, errp);
-	*count = ar.len;
-	return ret;
+	return do_blk_alloc(handle, inode, 0, goal, count, errp, 1);
 }
 
 ext4_fsblk_t ext4_new_blocks(handle_t *handle, struct inode *inode,
 				ext4_lblk_t iblock, ext4_fsblk_t goal,
 				unsigned long *count, int *errp)
 {
-	struct ext4_allocation_request ar;
-	ext4_fsblk_t ret;
-
-	if (!test_opt(inode->i_sb, MBALLOC)) {
-		ret = ext4_new_blocks_old(handle, inode, goal, count, errp);
-		return ret;
-	}
-
-	memset(&ar, 0, sizeof(ar));
-	/* Fill with neighbour allocated blocks */
-	ar.lleft  = 0;
-	ar.pleft  = 0;
-	ar.lright = 0;
-	ar.pright = 0;
-
-	ar.inode = inode;
-	ar.goal = goal;
-	ar.len = *count;
-	ar.logical = iblock;
-	if (S_ISREG(inode->i_mode))
-		ar.flags = EXT4_MB_HINT_DATA;
-	else
-		/* disable in-core preallocation for non-regular files */
-		ar.flags = 0;
-	ret = ext4_mb_new_blocks(handle, &ar, errp);
-	*count = ar.len;
-	return ret;
+	return do_blk_alloc(handle, inode, iblock, goal, count, errp, 0);
 }
 
-
 /**
  * ext4_count_free_blocks() -- count filesystem free blocks
  * @sb:		superblock
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 19d48dd..c401253 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1049,7 +1049,7 @@ extern ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 extern ext4_fsblk_t ext4_new_blocks(handle_t *handle, struct inode *inode,
 					ext4_lblk_t iblock, ext4_fsblk_t goal,
 					unsigned long *count, int *errp);
-extern ext4_fsblk_t ext4_new_blocks_old(handle_t *handle, struct inode *inode,
+extern ext4_fsblk_t ext4_orlov_new_blocks(handle_t *handle, struct inode *inode,
 			ext4_fsblk_t goal, unsigned long *count, int *errp);
 extern ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
 						ext4_fsblk_t nblocks);
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 09922ae..a810a21 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4048,7 +4048,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 	sbi = EXT4_SB(sb);
 
 	if (!test_opt(sb, MBALLOC)) {
-		block = ext4_new_blocks_old(handle, ar->inode, ar->goal,
+		block = ext4_orlov_new_blocks(handle, ar->inode, ar->goal,
 					    &(ar->len), errp);
 		return block;
 	}