ext4: mballoc avoid use root reserved blocks for non root allocation

mballoc allocation missed check for blocks reserved for root users. Add
ext4_has_free_blocks() check before allocation. Also modified
ext4_has_free_blocks() to support multiple block allocation request.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 33 insertions, 18 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 48787e86d438..25f63d8c1b3d 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1599,23 +1599,35 @@ out:
 
 /**
  * ext4_has_free_blocks()
- * @sbi:                in-core super block structure.
+ * @sbi:        in-core super block structure.
+ * @nblocks:    number of neeed blocks
  *
- * Check if filesystem has at least 1 free block available for allocation.
+ * Check if filesystem has free blocks available for allocation.
+ * Return the number of blocks avaible for allocation for this request
+ * On success, return nblocks
  */
-static int ext4_has_free_blocks(struct ext4_sb_info *sbi)
+ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
+                                                ext4_fsblk_t nblocks)
 {
-        ext4_fsblk_t free_blocks, root_blocks;
+        ext4_fsblk_t free_blocks;
+        ext4_fsblk_t root_blocks = 0;
 
         free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
-        root_blocks = ext4_r_blocks_count(sbi->s_es);
-        if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
+
+        if (!capable(CAP_SYS_RESOURCE) &&
                 sbi->s_resuid != current->fsuid &&
-                (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
-                return 0;
-        }
-        return 1;
-}
+                (sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
+                root_blocks = ext4_r_blocks_count(sbi->s_es);
+#ifdef CONFIG_SMP
+        if (free_blocks - root_blocks < FBC_BATCH)
+                free_blocks =
+                        percpu_counter_sum_positive(&sbi->s_freeblocks_counter);
+#endif
+        if (free_blocks - root_blocks < nblocks)
+                return free_blocks - root_blocks;
+        return nblocks;
+ }
+
 
 /**
  * ext4_should_retry_alloc()
@@ -1631,7 +1643,7 @@ static int ext4_has_free_blocks(struct ext4_sb_info *sbi)
  */
 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 {
-        if (!ext4_has_free_blocks(EXT4_SB(sb)) || (*retries)++ > 3)
+        if (!ext4_has_free_blocks(EXT4_SB(sb), 1) || (*retries)++ > 3)
                 return 0;
 
         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
@@ -1681,13 +1693,21 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
         ext4_group_t ngroups;
         unsigned long num = *count;
 
-        *errp = -ENOSPC;
         sb = inode->i_sb;
         if (!sb) {
+                *errp = -ENODEV;
                 printk("ext4_new_block: nonexistent device");
                 return 0;
         }
 
+        sbi = EXT4_SB(sb);
+        *count = ext4_has_free_blocks(sbi, *count);
+        if (*count == 0) {
+                *errp = -ENOSPC;
+                return 0;       /*return with ENOSPC error */
+        }
+        num = *count;
+
         /*
          * Check quota for allocation of this block.
          */
@@ -1711,11 +1731,6 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
         if (block_i && ((windowsz = block_i->rsv_window_node.rsv_goal_size) > 0))
                 my_rsv = &block_i->rsv_window_node;
 
-        if (!ext4_has_free_blocks(sbi)) {
-                *errp = -ENOSPC;
-                goto out;
-        }
-
         /*
          * First, test whether the goal block is free.
          */