From: Jan Kara <jack@suse.cz>
To: "zhangyi (F)" <yi.zhang@huawei.com>
Cc: Jan Kara <jack@suse.cz>,
tytso@mit.edu, linux-ext4@vger.kernel.org, luoshijie1@huawei.com,
zhangxiaoxu5@huawei.com
Subject: Re: [PATCH 2/2] jbd2: do not clear the BH_Mapped flag when forgetting a metadata buffer
Date: Wed, 12 Feb 2020 09:45:11 +0100 [thread overview]
Message-ID: <20200212084511.GA25573@quack2.suse.cz> (raw)
In-Reply-To: <6c03b515-d128-06be-2e38-56a01ee63263@huawei.com>
On Thu 06-02-20 23:28:01, zhangyi (F) wrote:
> Thanks for the comments.
>
> On 2020/2/6 19:46, Jan Kara wrote:
> > On Mon 03-02-20 22:04:58, zhangyi (F) wrote:
> [..]
> >> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> >> index 6396fe70085b..a649cdd1c5e5 100644
> >> --- a/fs/jbd2/commit.c
> >> +++ b/fs/jbd2/commit.c
> >> @@ -987,10 +987,13 @@ void jbd2_journal_commit_transaction(journal_t *journal)
> >> if (buffer_freed(bh) && !jh->b_next_transaction) {
> >> clear_buffer_freed(bh);
> >> clear_buffer_jbddirty(bh);
> >> - clear_buffer_mapped(bh);
> >> - clear_buffer_new(bh);
> >> - clear_buffer_req(bh);
> >> - bh->b_bdev = NULL;
> >> + if (buffer_unmap(bh)) {
> >> + clear_buffer_unmap(bh);
> >> + clear_buffer_mapped(bh);
> >> + clear_buffer_new(bh);
> >> + clear_buffer_req(bh);
> >> + bh->b_bdev = NULL;
> >> + }
> >
> > Any reason why you don't want to clear buffer_req and buffer_new flags for
> > all buffers as well? I agree that b_bdev setting and buffer_mapped need
> > special treatment.
> >
> IIUC, for the buffer coming from jbd2_journal_forget() is always 'block
> device backed' metadata buffer (not pretty sure), and for these metadata
Yes, it is.
> buffer, buffer_new flag will not be set. At the same time, since it's
> always mapped, so it's fine to keep the buffer_req flag even it's freed
> by the filesystem now, because it means the block device has committed
> this buffer, and it seems that it does not affect we reuse this buffer.
> Am I missing something ?
OK, you're right that buffer_new shouldn't be ever set for block backed
buffers and we don't care about buffer_req. So let's keep the split of bits
to clear as you did and just add a comment that for block device buffers it
is enough to clear buffer_jbddirty and buffer_freed, for file mapping
buffers (i.e., journalled data) we have to be more careful and clear more
bits.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2020-02-12 8:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-03 14:04 [PATCH 0/2] jbd2: fix an oops problem zhangyi (F)
2020-02-03 14:04 ` [PATCH 1/2] jbd2: move the clearing of b_modified flag to the journal_unmap_buffer() zhangyi (F)
2020-02-06 11:03 ` Jan Kara
2020-02-03 14:04 ` [PATCH 2/2] jbd2: do not clear the BH_Mapped flag when forgetting a metadata buffer zhangyi (F)
2020-02-06 11:46 ` Jan Kara
2020-02-06 15:28 ` zhangyi (F)
2020-02-12 8:45 ` Jan Kara [this message]
2020-02-11 6:51 ` zhangyi (F)
2020-02-12 8:47 ` Jan Kara
2020-02-12 13:14 ` zhangyi (F)
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