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SubjectRe: [PATCH] f2fs: update cur_valid_map_mir together with cur_valid_map
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Hi Yunlong,

On 2017/8/2 0:59, Yunlong Song wrote:
> Hi Chao,
> I think there is no need to test mirror bitmap when original bitmap's check
> get passed, it is an instruction waste for "test". By the way, previous patch
> uses WARN to skip trigger panic when the memory is flipped, I think it is proper
> to not trigger panic in this situation, because it is not code bug at all in
> such case.

Original idea is trying to use bitmap mirror to detect bitmap corruption caused
by memory overflow or bit-transition of cache.

So if we encounter inconsistency in between original bitmap and mirror bitmap,
there may be memory overflow or cache bit-transition, we need to detect that;
another case is that both bitmap is consistent, but we are trying to reuse valid
block address or free invalid block address, indeed that is a bug.

Below modification can cover above two cases, which make original idea of
introducing mirror bitmap check working correctly.

Thanks,

> On 08/01/2017 23:44, Chao Yu <mailto:chao@kernel.org> wrote:
>
> Hi Yunlong,
>
> How about checking consistence in between original and mirror bitmap all
> the time as below?
>
> ---
> fs/f2fs/segment.c | 41 +++++++++++++++++++++++++++--------------
> 1 file changed, 27 insertions(+), 14 deletions(-)
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index a26c24dae70c..f32a19cf486a 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1510,6 +1510,7 @@ static void update_sit_entry(struct f2fs_sb_info *sbi,
> block_t blkaddr, int del)
> struct seg_entry *se;
> unsigned int segno, offset;
> long int new_vblocks;
> + bool exist, mir_exist;
>
> segno = GET_SEGNO(sbi, blkaddr);
>
> @@ -1526,17 +1527,23 @@ static void update_sit_entry(struct f2fs_sb_info
> *sbi, block_t blkaddr, int del)
>
> /* Update valid block bitmap */
> if (del > 0) {
> - if (f2fs_test_and_set_bit(offset, se->cur_valid_map)) {
> + exist = f2fs_test_and_set_bit(offset, se->cur_valid_map);
> #ifdef CONFIG_F2FS_CHECK_FS
> - if (f2fs_test_and_set_bit(offset,
> - se->cur_valid_map_mir))
> - f2fs_bug_on(sbi, 1);
> - else
> - WARN_ON(1);
> -#else
> + mir_exist = f2fs_test_and_set_bit(offset,
> + se->cur_valid_map_mir);
> + if (exist != mir_exist) {
> + f2fs_msg(sbi->sb, KERN_ERR, "Inconsistent error "
> + "when setting bitmap, blk:%u, old bit:%d",
> + blkaddr, exist);
> f2fs_bug_on(sbi, 1);
> + }
> #endif
> + if (exist) {
> + f2fs_msg(sbi->sb, KERN_ERR,
> + "Bitmap was set, blk:%u", blkaddr);
> + f2fs_bug_on(sbi, 1);
> }
> +
> if (f2fs_discard_en(sbi) &&
> !f2fs_test_and_set_bit(offset, se->discard_map))
> sbi->discard_blks--;
> @@ -1547,17 +1554,23 @@ static void update_sit_entry(struct f2fs_sb_info
> *sbi, block_t blkaddr, int del)
> se->ckpt_valid_blocks++;
> }
> } else {
> - if (!f2fs_test_and_clear_bit(offset, se->cur_valid_map)) {
> + exist = f2fs_test_and_clear_bit(offset, se->cur_valid_map);
> #ifdef CONFIG_F2FS_CHECK_FS
> - if (!f2fs_test_and_clear_bit(offset,
> - se->cur_valid_map_mir))
> - f2fs_bug_on(sbi, 1);
> - else
> - WARN_ON(1);
> -#else
> + mir_exist = f2fs_test_and_clear_bit(offset,
> + se->cur_valid_map_mir);
> + if (exist != mir_exist) {
> + f2fs_msg(sbi->sb, KERN_ERR, "Inconsistent error "
> + "when clearing bitmap, blk:%u, old bit:%d",
> + blkaddr, exist);
> f2fs_bug_on(sbi, 1);
> + }
> #endif
> + if (!exist) {
> + f2fs_msg(sbi->sb, KERN_ERR,
> + "Bitmap was cleared, blk:%u", blkaddr);
> + f2fs_bug_on(sbi, 1);
> }
> +
> if (f2fs_discard_en(sbi) &&
> f2fs_test_and_clear_bit(offset, se->discard_map))
> sbi->discard_blks++;
> --
> 2.13.0.90.g1eb437020
>
> On 2017/8/1 15:56, Yunlong Song wrote:
> > When cur_valid_map passes the f2fs_test_and_set(,clear)_bit test,
> > cur_valid_map_mir update is skipped unlikely, so fix it.
> >
> > Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> > ---
> > fs/f2fs/segment.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 151968e..6f7731a 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1535,6 +1535,10 @@ static void update_sit_entry(struct f2fs_sb_info
> *sbi, block_t blkaddr, int del)
> > f2fs_bug_on(sbi, 1);
> > #endif
> > }
> > +#ifdef CONFIG_F2FS_CHECK_FS
> > + else
> > + f2fs_set_bit(offset, se->cur_valid_map_mir);
> > +#endif
> > if (f2fs_discard_en(sbi) &&
> > !f2fs_test_and_set_bit(offset, se->discard_map))
> > sbi->discard_blks--;
> > @@ -1556,6 +1560,10 @@ static void update_sit_entry(struct f2fs_sb_info
> *sbi, block_t blkaddr, int del)
> > f2fs_bug_on(sbi, 1);
> > #endif
> > }
> > +#ifdef CONFIG_F2FS_CHECK_FS
> > + else
> > + f2fs_clear_bit(offset, se->cur_valid_map_mir);
> > +#endif
> > if (f2fs_discard_en(sbi) &&
> > f2fs_test_and_clear_bit(offset, se->discard_map))
> > sbi->discard_blks++;
> >
>

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