[PATCH] ext3_get_blocks: support multiple blocks allocation in ext3_new_block()

Change ext3_try_to_allocate() (called via ext3_new_blocks()) to try to
allocate the requested number of blocks on a best effort basis: After
allocated the first block, it will always attempt to allocate the next few(up
to the requested size and not beyond the reservation window) adjacent blocks
at the same time.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 36 insertions, 10 deletions

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 46623f77666b..bba4aeb4a708 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -653,9 +653,11 @@ claim_block(spinlock_t *lock, int block, struct buffer_head *bh)
  */
 static int
 ext3_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
-        struct buffer_head *bitmap_bh, int goal, struct ext3_reserve_window *my_rsv)
+                        struct buffer_head *bitmap_bh, int goal,
+                        unsigned long *count, struct ext3_reserve_window *my_rsv)
 {
         int group_first_block, start, end;
+        unsigned long num = 0;
 
         /* we do allocation within the reservation window if we have a window */
         if (my_rsv) {
@@ -713,8 +715,18 @@ repeat:
                         goto fail_access;
                 goto repeat;
         }
-        return goal;
+        num++;
+        goal++;
+        while (num < *count && goal < end
+                && ext3_test_allocatable(goal, bitmap_bh)
+                && claim_block(sb_bgl_lock(EXT3_SB(sb), group), goal, bitmap_bh)) {
+                num++;
+                goal++;
+        }
+        *count = num;
+        return goal - num;
 fail_access:
+        *count = num;
         return -1;
 }
 
@@ -1024,11 +1036,12 @@ static int
 ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
                         unsigned int group, struct buffer_head *bitmap_bh,
                         int goal, struct ext3_reserve_window_node * my_rsv,
-                        int *errp)
+                        unsigned long *count, int *errp)
 {
         unsigned long group_first_block;
         int ret = 0;
         int fatal;
+        unsigned long num = *count;
 
         *errp = 0;
 
@@ -1051,7 +1064,8 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
          * or last attempt to allocate a block with reservation turned on failed
          */
         if (my_rsv == NULL ) {
-                ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh, goal, NULL);
+                ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh,
+                                                goal, count, NULL);
                 goto out;
         }
         /*
@@ -1093,11 +1107,13 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
                     || (my_rsv->rsv_end < group_first_block))
                         BUG();
                 ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh, goal,
-                                           &my_rsv->rsv_window);
+                                           &num, &my_rsv->rsv_window);
                 if (ret >= 0) {
-                        my_rsv->rsv_alloc_hit++;
+                        my_rsv->rsv_alloc_hit += num;
+                        *count = num;
                         break;                          /* succeed */
                 }
+                num = *count;
         }
 out:
         if (ret >= 0) {
@@ -1154,8 +1170,8 @@ int ext3_should_retry_alloc(struct super_block *sb, int *retries)
  * bitmap, and then for any free bit if that fails.
  * This function also updates quota and i_blocks field.
  */
-int ext3_new_block(handle_t *handle, struct inode *inode,
-                        unsigned long goal, int *errp)
+int ext3_new_blocks(handle_t *handle, struct inode *inode,
+                        unsigned long goal, unsigned long *count, int *errp)
 {
         struct buffer_head *bitmap_bh = NULL;
         struct buffer_head *gdp_bh;
@@ -1178,6 +1194,7 @@ int ext3_new_block(handle_t *handle, struct inode *inode,
         static int goal_hits, goal_attempts;
 #endif
         unsigned long ngroups;
+        unsigned long num = *count;
 
         *errp = -ENOSPC;
         sb = inode->i_sb;
@@ -1244,7 +1261,7 @@ retry:
                 if (!bitmap_bh)
                         goto io_error;
                 ret_block = ext3_try_to_allocate_with_rsv(sb, handle, group_no,
-                                        bitmap_bh, ret_block, my_rsv, &fatal);
+                                        bitmap_bh, ret_block, my_rsv, &num, &fatal);
                 if (fatal)
                         goto out;
                 if (ret_block >= 0)
@@ -1281,7 +1298,7 @@ retry:
                 if (!bitmap_bh)
                         goto io_error;
                 ret_block = ext3_try_to_allocate_with_rsv(sb, handle, group_no,
-                                        bitmap_bh, -1, my_rsv, &fatal);
+                                        bitmap_bh, -1, my_rsv, &num, &fatal);
                 if (fatal)
                         goto out;
                 if (ret_block >= 0) 
@@ -1388,6 +1405,7 @@ allocated:
 
         *errp = 0;
         brelse(bitmap_bh);
+        *count = num;
         return ret_block;
 
 io_error:
@@ -1406,6 +1424,14 @@ out:
         return 0;
 }
 
+int ext3_new_block(handle_t *handle, struct inode *inode,
+                        unsigned long goal, int *errp)
+{
+        unsigned long count = 1;
+
+        return ext3_new_blocks(handle, inode, goal, &count, errp);
+}
+
 unsigned long ext3_count_free_blocks(struct super_block *sb)
 {
         unsigned long desc_count;