ext4: teach ext4_mb_init_cache() to skip uptodate buddy caches

After online resize which adds new groups, some of the groups
in a buddy page may be initialized and uptodate, while other
(new ones) may be uninitialized.

The indication for init of new block groups is when ext4_mb_init_cache()
is called with an uptodate buddy page. In this case, initialized groups
on that buddy page must be skipped when initializing the buddy cache.

Signed-off-by: Amir Goldstein <amir73il@users.sf.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 25 insertions, 8 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 7311f25a88ea..1816eafb0a05 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -787,6 +787,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
         struct inode *inode;
         char *data;
         char *bitmap;
+        struct ext4_group_info *grinfo;
 
         mb_debug(1, "init page %lu\n", page->index);
 
@@ -819,6 +820,18 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
                 if (first_group + i >= ngroups)
                         break;
 
+                grinfo = ext4_get_group_info(sb, first_group + i);
+                /*
+                 * If page is uptodate then we came here after online resize
+                 * which added some new uninitialized group info structs, so
+                 * we must skip all initialized uptodate buddies on the page,
+                 * which may be currently in use by an allocating task.
+                 */
+                if (PageUptodate(page) && !EXT4_MB_GRP_NEED_INIT(grinfo)) {
+                        bh[i] = NULL;
+                        continue;
+                }
+
                 err = -EIO;
                 desc = ext4_get_group_desc(sb, first_group + i, NULL);
                 if (desc == NULL)
@@ -871,26 +884,28 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
         }
 
         /* wait for I/O completion */
-        for (i = 0; i < groups_per_page && bh[i]; i++)
-                wait_on_buffer(bh[i]);
+        for (i = 0; i < groups_per_page; i++)
+                if (bh[i])
+                        wait_on_buffer(bh[i]);
 
         err = -EIO;
-        for (i = 0; i < groups_per_page && bh[i]; i++)
-                if (!buffer_uptodate(bh[i]))
+        for (i = 0; i < groups_per_page; i++)
+                if (bh[i] && !buffer_uptodate(bh[i]))
                         goto out;
 
         err = 0;
         first_block = page->index * blocks_per_page;
-        /* init the page  */
-        memset(page_address(page), 0xff, PAGE_CACHE_SIZE);
         for (i = 0; i < blocks_per_page; i++) {
                 int group;
-                struct ext4_group_info *grinfo;
 
                 group = (first_block + i) >> 1;
                 if (group >= ngroups)
                         break;
 
+                if (!bh[group - first_group])
+                        /* skip initialized uptodate buddy */
+                        continue;
+
                 /*
                  * data carry information regarding this
                  * particular group in the format specified
@@ -919,6 +934,8 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
                          * incore got set to the group block bitmap below
                          */
                         ext4_lock_group(sb, group);
+                        /* init the buddy */
+                        memset(data, 0xff, blocksize);
                         ext4_mb_generate_buddy(sb, data, incore, group);
                         ext4_unlock_group(sb, group);
                         incore = NULL;
@@ -948,7 +965,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
 
 out:
         if (bh) {
-                for (i = 0; i < groups_per_page && bh[i]; i++)
+                for (i = 0; i < groups_per_page; i++)
                         brelse(bh[i]);
                 if (bh != &bhs)
                         kfree(bh);