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Message-Id: <1300985893-4371-4-git-send-email-amir73il@users.sourceforge.net>
Date: Thu, 24 Mar 2011 18:58:11 +0200
From: amir73il@...rs.sourceforge.net
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org, Amir Goldstein <amir73il@...rs.sf.net>
Subject: [PATCH v2 3/5] ext4: synchronize ext4_mb_init_group() with buddy page lock
From: Amir Goldstein <amir73il@...rs.sf.net>
The old routines ext4_mb_[get|put]_buddy_cache_lock(), which used
to take grp->alloc_sem for all groups on the buddy page have been
replaced with the routines ext4_mb_[get|put]_buddy_page_lock().
The new routines take both buddy and bitmap page locks to protect
against concurrent init of groups on the same buddy page.
The GROUP_NEED_INIT flag is tested again under page lock to check
if the group was initialized by another caller.
Signed-off-by: Amir Goldstein <amir73il@...rs.sf.net>
---
fs/ext4/mballoc.c | 177 +++++++++++++++++++----------------------------------
1 files changed, 63 insertions(+), 114 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index da52bd9..69601b2 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -957,22 +957,21 @@ out:
}
/*
- * 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
+ * Lock the buddy and bitmap pages. This make sure other parallel init_group
+ * on the same buddy page doesn't happen whild holding the buddy page lock.
+ * Return locked buddy and bitmap pages on e4b struct. If buddy and bitmap
+ * are on the same page e4b->bd_buddy_page is NULL and return value is 0.
*/
-static int ext4_mb_get_buddy_cache_lock(struct super_block *sb,
- ext4_group_t group)
+static int ext4_mb_get_buddy_page_lock(struct super_block *sb,
+ ext4_group_t group, struct ext4_buddy *e4b)
{
- int i;
- int block, pnum;
+ struct inode *inode = EXT4_SB(sb)->s_buddy_cache;
+ int block, pnum, poff;
int blocks_per_page;
- int groups_per_page;
- ext4_group_t ngroups = ext4_get_groups_count(sb);
- ext4_group_t first_group;
- struct ext4_group_info *grp;
+ struct page *page;
+
+ e4b->bd_buddy_page = NULL;
+ e4b->bd_bitmap_page = NULL;
blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
/*
@@ -982,57 +981,40 @@ static int ext4_mb_get_buddy_cache_lock(struct super_block *sb,
*/
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++) {
+ poff = block % blocks_per_page;
+ page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
+ if (!page)
+ return -EIO;
+ BUG_ON(page->mapping != inode->i_mapping);
+ e4b->bd_bitmap_page = page;
+ e4b->bd_bitmap = page_address(page) + (poff * sb->s_blocksize);
- if ((first_group + i) >= ngroups)
- 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_nested(&grp->alloc_sem, i);
+ if (blocks_per_page >= 2) {
+ /* buddy and bitmap are on the same page */
+ return 0;
}
- return i;
+
+ block++;
+ pnum = block / blocks_per_page;
+ poff = block % blocks_per_page;
+ page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
+ if (!page)
+ return -EIO;
+ BUG_ON(page->mapping != inode->i_mapping);
+ e4b->bd_buddy_page = page;
+ return 0;
}
-static void ext4_mb_put_buddy_cache_lock(struct super_block *sb,
- ext4_group_t group, int locked_group)
+static void ext4_mb_put_buddy_page_lock(struct ext4_buddy *e4b)
{
- 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);
+ if (e4b->bd_bitmap_page) {
+ unlock_page(e4b->bd_bitmap_page);
+ page_cache_release(e4b->bd_bitmap_page);
+ }
+ if (e4b->bd_buddy_page) {
+ unlock_page(e4b->bd_buddy_page);
+ page_cache_release(e4b->bd_buddy_page);
}
-
}
/*
@@ -1044,93 +1026,60 @@ static noinline_for_stack
int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)
{
- int ret = 0;
- 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;
+ struct ext4_buddy e4b;
+ struct page *page;
+ int ret = 0;
mb_debug(1, "init group %u\n", group);
- blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
this_grp = ext4_get_group_info(sb, group);
/*
* This ensures that we don't reinit the buddy cache
* page which map to the group from which we are already
* allocating. If we are looking at the buddy cache we would
* have taken a reference using ext4_mb_load_buddy and that
- * would have taken the alloc_sem lock.
+ * would have pinned buddy page to page cache.
*/
- num_grp_locked = ext4_mb_get_buddy_cache_lock(sb, group);
- if (!EXT4_MB_GRP_NEED_INIT(this_grp)) {
+ ret = ext4_mb_get_buddy_page_lock(sb, group, &e4b);
+ if (ret || !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)) {
+
+ page = e4b.bd_bitmap_page;
+ ret = ext4_mb_init_cache(page, NULL);
+ if (ret)
+ goto err;
+ if (!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 (e4b.bd_buddy_page == NULL) {
/*
* 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);
+ ret = 0;
+ goto err;
}
- if (page == NULL || !PageUptodate(page)) {
+ /* init buddy cache */
+ page = e4b.bd_buddy_page;
+ ret = ext4_mb_init_cache(page, e4b.bd_bitmap);
+ if (ret)
+ goto err;
+ if (!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);
+ ext4_mb_put_buddy_page_lock(&e4b);
return ret;
}
--
1.7.0.4
--
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