ext4: convert BUG_ON's to WARN_ON's in mballoc.c

If the in-core buddy bitmap gets corrupted (or out of sync with the
block bitmap), issue a WARN_ON and try to recover.  In most cases this
involves skipping trying to allocate out of a particular block group.
We can end up declaring the file system corrupted, which is fair,
since the file system probably should be checked before we proceed any
further.

Link: https://lore.kernel.org/r/20200414035649.293164-1-tytso@mit.edu
Google-Bug-Id: 34811296
Google-Bug-Id: 34639169
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 87c85be4c12e568d3d272cc8cf87f634ee13cf9a..30d5d97548c42117decfcca690f70b9b48dc490b 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1943,7 +1943,8 @@ void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
        int free;
 
        free = e4b->bd_info->bb_free;
-       BUG_ON(free <= 0);
+       if (WARN_ON(free <= 0))
+               return;
 
        i = e4b->bd_info->bb_first_free;
 
@@ -1966,7 +1967,8 @@ void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
                }
 
                mb_find_extent(e4b, i, ac->ac_g_ex.fe_len, &ex);
-               BUG_ON(ex.fe_len <= 0);
+               if (WARN_ON(ex.fe_len <= 0))
+                       break;
                if (free < ex.fe_len) {
                        ext4_grp_locked_error(sb, e4b->bd_group, 0, 0,
                                        "%d free clusters as per "