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Date: Mon, 20 Apr 2020 14:39:00 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Jan Kara <jack@...e.cz>, "zhangyi (F)" <yi.zhang@...wei.com>, Theodore Tso <tytso@....edu> Subject: [PATCH 5.4 22/60] jbd2: improve comments about freeing data buffers whose page mapping is NULL From: zhangyi (F) <yi.zhang@...wei.com> commit 780f66e59231fcf882f36c63f287252ee47cc75a upstream. Improve comments in jbd2_journal_commit_transaction() to describe why we don't need to clear the buffer_mapped bit for freeing file mapping buffers whose page mapping is NULL. Link: https://lore.kernel.org/r/20200217112706.20085-1-yi.zhang@huawei.com Fixes: c96dceeabf76 ("jbd2: do not clear the BH_Mapped flag when forgetting a metadata buffer") Suggested-by: Jan Kara <jack@...e.cz> Reviewed-by: Jan Kara <jack@...e.cz> Signed-off-by: zhangyi (F) <yi.zhang@...wei.com> Signed-off-by: Theodore Ts'o <tytso@....edu> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- fs/jbd2/commit.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -995,9 +995,10 @@ restart_loop: * journalled data) we need to unmap buffer and clear * more bits. We also need to be careful about the check * because the data page mapping can get cleared under - * out hands, which alse need not to clear more bits - * because the page and buffers will be freed and can - * never be reused once we are done with them. + * our hands. Note that if mapping == NULL, we don't + * need to make buffer unmapped because the page is + * already detached from the mapping and buffers cannot + * get reused. */ mapping = READ_ONCE(bh->b_page->mapping); if (mapping && !sb_is_blkdev_sb(mapping->host->i_sb)) {
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