handle-the-rest-of-ext4_mb_load_buddy-ENOMEM-errors

   1 ext4: handle the rest of ext4_mb_load_buddy() ENOMEM errors
   2
   3 From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
   4
   5 I've got another report about breaking ext4 by ENOMEM error returned from
   6 ext4_mb_load_buddy() caused by memory shortage in memory cgroup.
   7 This time inside ext4_discard_preallocations().
   8
   9 This patch replaces ext4_error() with ext4_warning() where errors returned
  10 from ext4_mb_load_buddy() are not fatal and handled by caller:
  11 * ext4_mb_discard_group_preallocations() - called before generating ENOSPC,
  12   we'll try to discard other group or return ENOSPC into user-space.
  13 * ext4_trim_all_free() - just stop trimming and return ENOMEM from ioctl.
  14
  15 Some callers cannot handle errors, thus __GFP_NOFAIL is used for them:
  16 * ext4_discard_preallocations()
  17 * ext4_mb_discard_lg_preallocations()
  18
  19 Fixes: adb7ef600cc9 ("ext4: use __GFP_NOFAIL in ext4_free_blocks()")
  20 Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
  21 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  22 ---
  23  fs/ext4/mballoc.c | 23 ++++++++++++++---------
  24  1 file changed, 14 insertions(+), 9 deletions(-)
  25
  26 diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
  27 index 5083bce20ac4..b7928cddd539 100644
  28 --- a/fs/ext4/mballoc.c
  29 +++ b/fs/ext4/mballoc.c
  30 @@ -3887,7 +3887,8 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
  31
  32         err = ext4_mb_load_buddy(sb, group, &e4b);
  33         if (err) {
  34 -               ext4_error(sb, "Error loading buddy information for %u", group);
  35 +               ext4_warning(sb, "Error %d loading buddy information for %u",
  36 +                            err, group);
  37                 put_bh(bitmap_bh);
  38                 return 0;
  39         }
  40 @@ -4044,10 +4045,11 @@ void ext4_discard_preallocations(struct inode *inode)
  41                 BUG_ON(pa->pa_type != MB_INODE_PA);
  42                 group = ext4_get_group_number(sb, pa->pa_pstart);
  43
  44 -               err = ext4_mb_load_buddy(sb, group, &e4b);
  45 +               err = ext4_mb_load_buddy_gfp(sb, group, &e4b,
  46 +                                            GFP_NOFS|__GFP_NOFAIL);
  47                 if (err) {
  48 -                       ext4_error(sb, "Error loading buddy information for %u",
  49 -                                       group);
  50 +                       ext4_error(sb, "Error %d loading buddy information for %u",
  51 +                                  err, group);
  52                         continue;
  53                 }
  54
  55 @@ -4303,11 +4305,14 @@ ext4_mb_discard_lg_preallocations(struct super_block *sb,
  56         spin_unlock(&lg->lg_prealloc_lock);
  57
  58         list_for_each_entry_safe(pa, tmp, &discard_list, u.pa_tmp_list) {
  59 +               int err;
  60
  61                 group = ext4_get_group_number(sb, pa->pa_pstart);
  62 -               if (ext4_mb_load_buddy(sb, group, &e4b)) {
  63 -                       ext4_error(sb, "Error loading buddy information for %u",
  64 -                                       group);
  65 +               err = ext4_mb_load_buddy_gfp(sb, group, &e4b,
  66 +                                            GFP_NOFS|__GFP_NOFAIL);
  67 +               if (err) {
  68 +                       ext4_error(sb, "Error %d loading buddy information for %u",
  69 +                                  err, group);
  70                         continue;
  71                 }
  72                 ext4_lock_group(sb, group);
  73 @@ -5127,8 +5132,8 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
  74
  75         ret = ext4_mb_load_buddy(sb, group, &e4b);
  76         if (ret) {
  77 -               ext4_error(sb, "Error in loading buddy "
  78 -                               "information for %u", group);
  79 +               ext4_warning(sb, "Error %d loading buddy information for %u",
  80 +                            ret, group);
  81                 return ret;
  82         }
  83         bitmap = e4b.bd_bitmap;