Messages in this thread Patch in this message | | | Subject | Re: [PATCH 1/2] f2fs: fix to avoid potential negative .f_bfree | From | Chao Yu <> | Date | Tue, 30 Apr 2019 11:14:59 +0800 |
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On 2019/4/30 10:54, Jaegeuk Kim wrote: > On 04/29, Chao Yu wrote: >> On 2019-4-28 21:47, Jaegeuk Kim wrote: >>> On 04/26, Chao Yu wrote: >>>> When calculating .f_bfree value in f2fs_statfs(), sbi->unusable_block_count >>>> can be increased after the judgment condition, result in overflow of >>>> .f_bfree in later calculation. This patch fixes to use a temporary signed >>>> variable to save the calculation result of .f_bfree. >>>> >>>> if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) >>>> buf->f_bfree = 0; >>>> else >>>> buf->f_bfree -= sbi->unusable_block_count; >>> >>> Do we just need stat_lock for this? >> >> Like we access other stat value in statfs(), we just need the instantaneous >> value of .unusable_block_count, so we don't need additional stat_lock, right? > > What I've concerend is whether or not this fixes all the inconsistent values. > The original intention was providing stats in best effort, so we wouldn't use > any lock.
Hmm.. I've made a patch to protect .unusable_block_count update/access as below, how about merging this two patch, in addition, in this patch, let's add stat_lock around accessing .f_bfree/.unusable_block_count.
From b927209d10fc222243037d05ccc899f48569e773 Mon Sep 17 00:00:00 2001 From: Chao Yu <yuchao0@huawei.com> Date: Fri, 26 Apr 2019 15:51:22 +0800 Subject: [PATCH] f2fs: fix to cover sbi->unusable_block_count with stat_lock
Signed-off-by: Chao Yu <yuchao0@huawei.com> --- fs/f2fs/checkpoint.c | 4 ++++ fs/f2fs/segment.c | 5 ++++- fs/f2fs/super.c | 2 ++ 3 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c index f6ba9a743a2d..526a70ea7433 100644 --- a/fs/f2fs/checkpoint.c +++ b/fs/f2fs/checkpoint.c @@ -1536,7 +1536,11 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) clear_sbi_flag(sbi, SBI_IS_DIRTY); clear_sbi_flag(sbi, SBI_NEED_CP); clear_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH); + + spin_lock(&sbi->stat_lock); sbi->unusable_block_count = 0; + spin_unlock(&sbi->stat_lock); + __set_cp_next_pack(sbi);
/* diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 5c3f07540db1..f10c394cf467 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -2203,8 +2203,11 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del) * before, we must track that to know how much space we * really have. */ - if (f2fs_test_bit(offset, se->ckpt_valid_map)) + if (f2fs_test_bit(offset, se->ckpt_valid_map)) { + spin_lock(&sbi->stat_lock); sbi->unusable_block_count++; + spin_unlock(&sbi->stat_lock); + } }
if (f2fs_test_and_clear_bit(offset, se->discard_map)) diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 1a05a636bd2a..dd6e7b351b58 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -1546,7 +1546,9 @@ static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi) set_sbi_flag(sbi, SBI_CP_DISABLED); f2fs_write_checkpoint(sbi, &cpc);
+ spin_lock(&sbi->stat_lock); sbi->unusable_block_count = 0; + spin_unlock(&sbi->stat_lock); mutex_unlock(&sbi->gc_mutex); restore_flag: sbi->sb->s_flags = s_flags; /* Restore MS_RDONLY status */ -- 2.18.0.rc1
> >> >> Thanks, >> >>> >>>> >>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> >>>> --- >>>> fs/f2fs/super.c | 7 +++++-- >>>> 1 file changed, 5 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c >>>> index 2376bb01b5c4..fcc9793dbc2c 100644 >>>> --- a/fs/f2fs/super.c >>>> +++ b/fs/f2fs/super.c >>>> @@ -1216,6 +1216,7 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) >>>> u64 id = huge_encode_dev(sb->s_bdev->bd_dev); >>>> block_t total_count, user_block_count, start_count; >>>> u64 avail_node_count; >>>> + long long bfree; >>>> >>>> total_count = le64_to_cpu(sbi->raw_super->block_count); >>>> user_block_count = sbi->user_block_count; >>>> @@ -1226,10 +1227,12 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) >>>> buf->f_blocks = total_count - start_count; >>>> buf->f_bfree = user_block_count - valid_user_blocks(sbi) - >>>> sbi->current_reserved_blocks; >>>> - if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) >>>> + >>>> + bfree = buf->f_bfree - sbi->unusable_block_count; >>>> + if (unlikely(bfree < 0)) >>>> buf->f_bfree = 0; >>>> else >>>> - buf->f_bfree -= sbi->unusable_block_count; >>>> + buf->f_bfree = bfree; >>>> >>>> if (buf->f_bfree > F2FS_OPTION(sbi).root_reserved_blocks) >>>> buf->f_bavail = buf->f_bfree - >>>> -- >>>> 2.18.0.rc1 > . >
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