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From: Theodore Y. Ts'o <tytso@mit.edu>
To: Mauricio Faria de Oliveira <mfo@canonical.com>
Cc: linux-ext4@vger.kernel.org, ocfs2-devel@oss.oracle.com,
	Jan Kara <jack@suse.cz>, Andreas Dilger <adilger@dilger.ca>,
	dann frazier <dann.frazier@canonical.com>,
	Joseph Qi <joseph.qi@linux.alibaba.com>
Subject: [Ocfs2-devel] [PATCH v5 3/4] ext4: data=journal: fixes for ext4_page_mkwrite()
Date: Thu, 8 Oct 2020 22:10:11 -0400	[thread overview]
Message-ID: <20201009021011.GG235506@mit.edu> (raw)
In-Reply-To: <20201006004841.600488-4-mfo@canonical.com>

On Mon, Oct 05, 2020 at 09:48:40PM -0300, Mauricio Faria de Oliveira wrote:
> These are two fixes for data journalling required by
> the next patch, discovered while testing it.
> 
> First, the optimization to return early if all buffers
> are mapped is not appropriate for the next patch:
> 
> The inode _must_ be added to the transaction's list in
> data=journal mode (so to write-protect pages on commit)
> thus we cannot return early there.
> 
> Second, once that optimization to reduce transactions
> was disabled for data=journal mode, more transactions
> happened, and occasionally hit this warning message:
> 'JBD2: Spotted dirty metadata buffer'.
> 
> Reason is, block_page_mkwrite() will set_buffer_dirty()
> before do_journal_get_write_access() that is there to
> prevent it. This issue was masked by the optimization.
> 
> So, on data=journal use __block_write_begin() instead.
> This also requires page locking and len recalculation.
> (see block_page_mkwrite() for implementation details.)
> 
> Finally, as Jan noted there is little sharing between
> data=journal and other modes in ext4_page_mkwrite().
> 
> However, a prototype of ext4_journalled_page_mkwrite()
> showed there still would be lots of duplicated lines
> (tens of) that didn't seem worth it.
> 
> Thus this patch ends up with an ugly goto to skip all
> non-data journalling code (to avoid long indentations,
> but that can be changed..) in the beginning, and just
> a conditional in the transaction section.
> 
> Well, we skip a common part to data journalling which
> is the page truncated check, but we do it again after
> ext4_journal_start() when we re-acquire the page lock
> (so not to acquire the page lock twice needlessly for
> data journalling.)
> 
> Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
> Suggested-by: Jan Kara <jack@suse.cz>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Reviewed-by: Andreas Dilger <adilger@dilger.ca>

Thanks, applied.

				- Ted

  reply	other threads:[~2020-10-09  2:10 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-06  0:48 [Ocfs2-devel] [PATCH v5 0/4] ext4/jbd2: data=journal: write-protect pages on transaction commit Mauricio Faria de Oliveira
2020-10-06  0:48 ` [Ocfs2-devel] [PATCH v5 1/4] jbd2: introduce/export functions jbd2_journal_submit|finish_inode_data_buffers() Mauricio Faria de Oliveira
2020-10-09  2:05   ` Theodore Y. Ts'o
2020-10-06  0:48 ` [Ocfs2-devel] [PATCH v5 2/4] jbd2, ext4, ocfs2: introduce/use journal callbacks j_submit|finish_inode_data_buffers() Mauricio Faria de Oliveira
2020-10-09  2:08   ` Theodore Y. Ts'o
2020-10-06  0:48 ` [Ocfs2-devel] [PATCH v5 3/4] ext4: data=journal: fixes for ext4_page_mkwrite() Mauricio Faria de Oliveira
2020-10-09  2:10   ` Theodore Y. Ts'o [this message]
2020-10-06  0:48 ` [Ocfs2-devel] [PATCH v5 4/4] ext4: data=journal: write-protect pages on j_submit_inode_data_buffers() Mauricio Faria de Oliveira
2020-10-09  2:10   ` Theodore Y. Ts'o

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