ext4: Don't claim block from group which has corrupt bitmap

In ext4_mb_complex_scan_group, if the extent length of the newly
found extentet is greater than than the total free blocks counted
in group info, break without claiming the block.

Document different ext4_error usage, explaining the state with which we
continue if we mount with errors=continue

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 2121184a3fa502574da27d48b9d9cbb9b60a90f8..6968c53e62ad5a8406f4bdf9bafdfaa8c06af955 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -967,6 +967,10 @@ static void ext4_mb_generate_buddy(struct super_block *sb,
                ext4_error(sb, __FUNCTION__,
                        "EXT4-fs: group %lu: %u blocks in bitmap, %u in gd\n",
                        group, free, grp->bb_free);
+               /*
+                * If we intent to continue, we consider group descritor
+                * corrupt and update bb_free using bitmap value
+                */
                grp->bb_free = free;
        }
 
@@ -1822,7 +1826,7 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
                                                EXT4_BLOCKS_PER_GROUP(sb), i);
                if (i >= EXT4_BLOCKS_PER_GROUP(sb)) {
                        /*
-                        * IF we corrupt the bitmap  we won't find any
+                        * IF we have corrupt bitmap, we won't find any
                         * free blocks even though group info says we
                         * we have free blocks
                         */
@@ -1838,6 +1842,12 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
                        ext4_error(sb, __FUNCTION__, "%d free blocks as per "
                                        "group info. But got %d blocks\n",
                                        free, ex.fe_len);
+                       /*
+                        * The number of free blocks differs. This mostly
+                        * indicate that the bitmap is corrupt. So exit
+                        * without claiming the space.
+                        */
+                       break;
                }
 
                ext4_mb_measure_extent(ac, &ex, e4b);
@@ -3771,6 +3781,10 @@ static int ext4_mb_release_inode_pa(struct ext4_buddy *e4b,
                        (unsigned long) pa->pa_len);
                ext4_error(sb, __FUNCTION__, "free %u, pa_free %u\n",
                                                free, pa->pa_free);
+               /*
+                * pa is already deleted so we use the value obtained
+                * from the bitmap and continue.
+                */
        }
        atomic_add(free, &sbi->s_mb_discarded);
        if (ac)