diff options
| author | Ojaswin Mujoo <ojaswin@linux.ibm.com> | 2023-06-09 16:04:03 +0530 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2023-07-23 08:21:14 -0400 |
| commit | 5d5460fa7932bed3a9082a6a8852cfbdb46acbe8 (patch) | |
| tree | 505e88e2dd22fc21f5e7308de39d841aa7232a61 | |
| parent | 6909cf5c4101214f4305a62d582a5b93c7e1eb9a (diff) | |
ext4: fix off by one issue in ext4_mb_choose_next_group_best_avail()
In ext4_mb_choose_next_group_best_avail(), we want the start order to be
1 less than goal length and the min_order to be, at max, 1 more than the
original length. This commit fixes an off by one issue that arose due to
the fact that 1 << fls(n) > (n).
After all the processing:
order = 1 order below goal len
min_order = maximum of the three:-
- order - trim_order
- 1 order below B2C(s_stripe)
- 1 order above original len
Cc: stable@kernel.org
Fixes: 33122aa930 ("ext4: Add allocation criteria 1.5 (CR1_5)")
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20230609103403.112807-1-ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | fs/ext4/mballoc.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index a2475b8c9fb5..456150ef6111 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1006,14 +1006,11 @@ static void ext4_mb_choose_next_group_best_avail(struct ext4_allocation_context * fls() instead since we need to know the actual length while modifying * goal length. */ - order = fls(ac->ac_g_ex.fe_len); + order = fls(ac->ac_g_ex.fe_len) - 1; min_order = order - sbi->s_mb_best_avail_max_trim_order; if (min_order < 0) min_order = 0; - if (1 << min_order < ac->ac_o_ex.fe_len) - min_order = fls(ac->ac_o_ex.fe_len) + 1; - if (sbi->s_stripe > 0) { /* * We are assuming that stripe size is always a multiple of @@ -1021,9 +1018,16 @@ static void ext4_mb_choose_next_group_best_avail(struct ext4_allocation_context */ num_stripe_clusters = EXT4_NUM_B2C(sbi, sbi->s_stripe); if (1 << min_order < num_stripe_clusters) - min_order = fls(num_stripe_clusters); + /* + * We consider 1 order less because later we round + * up the goal len to num_stripe_clusters + */ + min_order = fls(num_stripe_clusters) - 1; } + if (1 << min_order < ac->ac_o_ex.fe_len) + min_order = fls(ac->ac_o_ex.fe_len); + for (i = order; i >= min_order; i--) { int frag_order; /* |