releases/4.4.18/ext4-fix-reference-counting-bug-on-block-allocation-error.patch

   1 From 554a5ccc4e4a20c5f3ec859de0842db4b4b9c77e Mon Sep 17 00:00:00 2001
   2 From: Vegard Nossum <vegard.nossum@oracle.com>
   3 Date: Thu, 14 Jul 2016 23:02:47 -0400
   4 Subject: ext4: fix reference counting bug on block allocation error
   5
   6 From: Vegard Nossum <vegard.nossum@oracle.com>
   7
   8 commit 554a5ccc4e4a20c5f3ec859de0842db4b4b9c77e upstream.
   9
  10 If we hit this error when mounted with errors=continue or
  11 errors=remount-ro:
  12
  13     EXT4-fs error (device loop0): ext4_mb_mark_diskspace_used:2940: comm ext4.exe: Allocating blocks 5090-6081 which overlap fs metadata
  14
  15 then ext4_mb_new_blocks() will call ext4_mb_release_context() and try to
  16 continue. However, ext4_mb_release_context() is the wrong thing to call
  17 here since we are still actually using the allocation context.
  18
  19 Instead, just error out. We could retry the allocation, but there is a
  20 possibility of getting stuck in an infinite loop instead, so this seems
  21 safer.
  22
  23 [ Fixed up so we don't return EAGAIN to userspace. --tytso ]
  24
  25 Fixes: 8556e8f3b6 ("ext4: Don't allow new groups to be added during block allocation")
  26 Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
  27 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  28 Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30
  31 ---
  32  fs/ext4/mballoc.c |   17 +++--------------
  33  1 file changed, 3 insertions(+), 14 deletions(-)
  34
  35 --- a/fs/ext4/mballoc.c
  36 +++ b/fs/ext4/mballoc.c
  37 @@ -2932,7 +2932,7 @@ ext4_mb_mark_diskspace_used(struct ext4_
  38                 ext4_error(sb, "Allocating blocks %llu-%llu which overlap "
  39                            "fs metadata", block, block+len);
  40                 /* File system mounted not to panic on error
  41 -                * Fix the bitmap and repeat the block allocation
  42 +                * Fix the bitmap and return EFSCORRUPTED
  43                  * We leak some of the blocks here.
  44                  */
  45                 ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  46 @@ -2941,7 +2941,7 @@ ext4_mb_mark_diskspace_used(struct ext4_
  47                 ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
  48                 err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
  49                 if (!err)
  50 -                       err = -EAGAIN;
  51 +                       err = -EFSCORRUPTED;
  52                 goto out_err;
  53         }
  54
  55 @@ -4506,18 +4506,7 @@ repeat:
  56         }
  57         if (likely(ac->ac_status == AC_STATUS_FOUND)) {
  58                 *errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_clstrs);
  59 -               if (*errp == -EAGAIN) {
  60 -                       /*
  61 -                        * drop the reference that we took
  62 -                        * in ext4_mb_use_best_found
  63 -                        */
  64 -                       ext4_mb_release_context(ac);
  65 -                       ac->ac_b_ex.fe_group = 0;
  66 -                       ac->ac_b_ex.fe_start = 0;
  67 -                       ac->ac_b_ex.fe_len = 0;
  68 -                       ac->ac_status = AC_STATUS_CONTINUE;
  69 -                       goto repeat;
  70 -               } else if (*errp) {
  71 +               if (*errp) {
  72                         ext4_discard_allocated_blocks(ac);
  73                         goto errout;
  74                 } else {