ext4: Use EXT4_GROUP_INFO_NEED_INIT_BIT during resize

The new groups added during resize are flagged as
need_init group. Make sure we properly initialize these
groups. When we have block size < page size and we are adding
new groups the page may still be marked uptodate even though
we haven't initialized the group. While forcing the init
of buddy cache we need to make sure other groups part of the
same page of buddy cache is not using the cache.
group_info->alloc_sem is added to ensure the same.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
cc: stable@kernel.org

1 files changed, 202 insertions, 59 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index edf9730ba72..d2b1bcaf88e 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -886,18 +886,20 @@ static noinline_for_stack int
 ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
 					struct ext4_buddy *e4b)
 {
-	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	struct inode *inode = sbi->s_buddy_cache;
 	int blocks_per_page;
 	int block;
 	int pnum;
 	int poff;
 	struct page *page;
 	int ret;
+	struct ext4_group_info *grp;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct inode *inode = sbi->s_buddy_cache;
 
 	mb_debug("load group %u\n", group);
 
 	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
+	grp = ext4_get_group_info(sb, group);
 
 	e4b->bd_blkbits = sb->s_blocksize_bits;
 	e4b->bd_info = ext4_get_group_info(sb, group);
@@ -905,6 +907,15 @@ ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
 	e4b->bd_group = group;
 	e4b->bd_buddy_page = NULL;
 	e4b->bd_bitmap_page = NULL;
+	e4b->alloc_semp = &grp->alloc_sem;
+
+	/* Take the read lock on the group alloc
+	 * sem. This would make sure a parallel
+	 * ext4_mb_init_group happening on other
+	 * groups mapped by the page is blocked
+	 * till we are done with allocation
+	 */
+	down_read(e4b->alloc_semp);
 
 	/*
 	 * the buddy cache inode stores the block bitmap
@@ -920,6 +931,14 @@ ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
 	page = find_get_page(inode->i_mapping, pnum);
 	if (page == NULL || !PageUptodate(page)) {
 		if (page)
+			/*
+			 * drop the page reference and try
+			 * to get the page with lock. If we
+			 * are not uptodate that implies
+			 * somebody just created the page but
+			 * is yet to initialize the same. So
+			 * wait for it to initialize.
+			 */
 			page_cache_release(page);
 		page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
 		if (page) {
@@ -985,6 +1004,9 @@ err:
 		page_cache_release(e4b->bd_buddy_page);
 	e4b->bd_buddy = NULL;
 	e4b->bd_bitmap = NULL;
+
+	/* Done with the buddy cache */
+	up_read(e4b->alloc_semp);
 	return ret;
 }
 
@@ -994,6 +1016,8 @@ static void ext4_mb_release_desc(struct ext4_buddy *e4b)
 		page_cache_release(e4b->bd_bitmap_page);
 	if (e4b->bd_buddy_page)
 		page_cache_release(e4b->bd_buddy_page);
+	/* Done with the buddy cache */
+	up_read(e4b->alloc_semp);
 }
 
 
@@ -1696,6 +1720,173 @@ static int ext4_mb_good_group(struct ext4_allocation_context *ac,
 	return 0;
 }
 
+/*
+ * lock the group_info alloc_sem of all the groups
+ * belonging to the same buddy cache page. This
+ * make sure other parallel operation on the buddy
+ * cache doesn't happen  whild holding the buddy cache
+ * lock
+ */
+int ext4_mb_get_buddy_cache_lock(struct super_block *sb, ext4_group_t group)
+{
+	int i;
+	int block, pnum;
+	int blocks_per_page;
+	int groups_per_page;
+	ext4_group_t first_group;
+	struct ext4_group_info *grp;
+
+	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
+	/*
+	 * the buddy cache inode stores the block bitmap
+	 * and buddy information in consecutive blocks.
+	 * So for each group we need two blocks.
+	 */
+	block = group * 2;
+	pnum = block / blocks_per_page;
+	first_group = pnum * blocks_per_page / 2;
+
+	groups_per_page = blocks_per_page >> 1;
+	if (groups_per_page == 0)
+		groups_per_page = 1;
+	/* read all groups the page covers into the cache */
+	for (i = 0; i < groups_per_page; i++) {
+
+		if ((first_group + i) >= EXT4_SB(sb)->s_groups_count)
+			break;
+		grp = ext4_get_group_info(sb, first_group + i);
+		/* take all groups write allocation
+		 * semaphore. This make sure there is
+		 * no block allocation going on in any
+		 * of that groups
+		 */
+		down_write(&grp->alloc_sem);
+	}
+	return i;
+}
+
+void ext4_mb_put_buddy_cache_lock(struct super_block *sb,
+					ext4_group_t group, int locked_group)
+{
+	int i;
+	int block, pnum;
+	int blocks_per_page;
+	ext4_group_t first_group;
+	struct ext4_group_info *grp;
+
+	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
+	/*
+	 * the buddy cache inode stores the block bitmap
+	 * and buddy information in consecutive blocks.
+	 * So for each group we need two blocks.
+	 */
+	block = group * 2;
+	pnum = block / blocks_per_page;
+	first_group = pnum * blocks_per_page / 2;
+	/* release locks on all the groups */
+	for (i = 0; i < locked_group; i++) {
+
+		grp = ext4_get_group_info(sb, first_group + i);
+		/* take all groups write allocation
+		 * semaphore. This make sure there is
+		 * no block allocation going on in any
+		 * of that groups
+		 */
+		up_write(&grp->alloc_sem);
+	}
+
+}
+
+static int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)
+{
+
+	int ret;
+	void *bitmap;
+	int blocks_per_page;
+	int block, pnum, poff;
+	int num_grp_locked = 0;
+	struct ext4_group_info *this_grp;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct inode *inode = sbi->s_buddy_cache;
+	struct page *page = NULL, *bitmap_page = NULL;
+
+	mb_debug("init group %lu\n", group);
+	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
+	this_grp = ext4_get_group_info(sb, group);
+	/*
+	 * This ensures we don't add group
+	 * to this buddy cache via resize
+	 */
+	num_grp_locked =  ext4_mb_get_buddy_cache_lock(sb, group);
+	if (!EXT4_MB_GRP_NEED_INIT(this_grp)) {
+		/*
+		 * somebody initialized the group
+		 * return without doing anything
+		 */
+		ret = 0;
+		goto err;
+	}
+	/*
+	 * the buddy cache inode stores the block bitmap
+	 * and buddy information in consecutive blocks.
+	 * So for each group we need two blocks.
+	 */
+	block = group * 2;
+	pnum = block / blocks_per_page;
+	poff = block % blocks_per_page;
+	page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
+	if (page) {
+		BUG_ON(page->mapping != inode->i_mapping);
+		ret = ext4_mb_init_cache(page, NULL);
+		if (ret) {
+			unlock_page(page);
+			goto err;
+		}
+		unlock_page(page);
+	}
+	if (page == NULL || !PageUptodate(page)) {
+		ret = -EIO;
+		goto err;
+	}
+	mark_page_accessed(page);
+	bitmap_page = page;
+	bitmap = page_address(page) + (poff * sb->s_blocksize);
+
+	/* init buddy cache */
+	block++;
+	pnum = block / blocks_per_page;
+	poff = block % blocks_per_page;
+	page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
+	if (page == bitmap_page) {
+		/*
+		 * If both the bitmap and buddy are in
+		 * the same page we don't need to force
+		 * init the buddy
+		 */
+		unlock_page(page);
+	} else if (page) {
+		BUG_ON(page->mapping != inode->i_mapping);
+		ret = ext4_mb_init_cache(page, bitmap);
+		if (ret) {
+			unlock_page(page);
+			goto err;
+		}
+		unlock_page(page);
+	}
+	if (page == NULL || !PageUptodate(page)) {
+		ret = -EIO;
+		goto err;
+	}
+	mark_page_accessed(page);
+err:
+	ext4_mb_put_buddy_cache_lock(sb, group, num_grp_locked);
+	if (bitmap_page)
+		page_cache_release(bitmap_page);
+	if (page)
+		page_cache_release(page);
+	return ret;
+}
+
 static noinline_for_stack int
 ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
 {
@@ -1779,7 +1970,7 @@ repeat:
 				group = 0;
 
 			/* quick check to skip empty groups */
-			grp = ext4_get_group_info(ac->ac_sb, group);
+			grp = ext4_get_group_info(sb, group);
 			if (grp->bb_free == 0)
 				continue;
 
@@ -1792,10 +1983,9 @@ repeat:
 				 * we need full data about the group
 				 * to make a good selection
 				 */
-				err = ext4_mb_load_buddy(sb, group, &e4b);
+				err = ext4_mb_init_group(sb, group);
 				if (err)
 					goto out;
-				ext4_mb_release_desc(&e4b);
 			}
 
 			/*
@@ -2246,7 +2436,7 @@ ext4_mb_store_history(struct ext4_allocation_context *ac)
 
 
 /* Create and initialize ext4_group_info data for the given group. */
-static int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
+int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
 			  struct ext4_group_desc *desc)
 {
 	int i, len;
@@ -2304,6 +2494,7 @@ static int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
 	}
 
 	INIT_LIST_HEAD(&meta_group_info[i]->bb_prealloc_list);
+	init_rwsem(&meta_group_info[i]->alloc_sem);
 	meta_group_info[i]->bb_free_root.rb_node = NULL;;
 
 #ifdef DOUBLE_CHECK
@@ -2331,54 +2522,6 @@ exit_meta_group_info:
 } /* ext4_mb_add_groupinfo */
 
 /*
- * Add a group to the existing groups.
- * This function is used for online resize
- */
-int ext4_mb_add_more_groupinfo(struct super_block *sb, ext4_group_t group,
-			       struct ext4_group_desc *desc)
-{
-	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	struct inode *inode = sbi->s_buddy_cache;
-	int blocks_per_page;
-	int block;
-	int pnum;
-	struct page *page;
-	int err;
-
-	/* Add group based on group descriptor*/
-	err = ext4_mb_add_groupinfo(sb, group, desc);
-	if (err)
-		return err;
-
-	/*
-	 * Cache pages containing dynamic mb_alloc datas (buddy and bitmap
-	 * datas) are set not up to date so that they will be re-initilaized
-	 * during the next call to ext4_mb_load_buddy
-	 */
-
-	/* Set buddy page as not up to date */
-	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
-	block = group * 2;
-	pnum = block / blocks_per_page;
-	page = find_get_page(inode->i_mapping, pnum);
-	if (page != NULL) {
-		ClearPageUptodate(page);
-		page_cache_release(page);
-	}
-
-	/* Set bitmap page as not up to date */
-	block++;
-	pnum = block / blocks_per_page;
-	page = find_get_page(inode->i_mapping, pnum);
-	if (page != NULL) {
-		ClearPageUptodate(page);
-		page_cache_release(page);
-	}
-
-	return 0;
-}
-
-/*
  * Update an existing group.
  * This function is used for online resize
  */
@@ -4588,11 +4731,6 @@ do_more:
 	err = ext4_journal_get_write_access(handle, gd_bh);
 	if (err)
 		goto error_return;
-
-	err = ext4_mb_load_buddy(sb, block_group, &e4b);
-	if (err)
-		goto error_return;
-
 #ifdef AGGRESSIVE_CHECK
 	{
 		int i;
@@ -4606,6 +4744,8 @@ do_more:
 	/* We dirtied the bitmap block */
 	BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
 	err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
+	if (err)
+		goto error_return;
 
 	if (ac) {
 		ac->ac_b_ex.fe_group = block_group;
@@ -4614,6 +4754,9 @@ do_more:
 		ext4_mb_store_history(ac);
 	}
 
+	err = ext4_mb_load_buddy(sb, block_group, &e4b);
+	if (err)
+		goto error_return;
 	if (metadata && ext4_handle_valid(handle)) {
 		/* blocks being freed are metadata. these blocks shouldn't
 		 * be used until this transaction is committed */