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Date: Wed, 6 Jan 2021 14:05:26 -0800 From: "Darrick J. Wong" <darrick.wong@...cle.com> To: Daejun Park <daejun7.park@...sung.com> Cc: "tytso@....edu" <tytso@....edu>, "adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>, "harshadshirwadkar@...il.com" <harshadshirwadkar@...il.com>, "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] ext4: Remove expensive flush on fast commit On Wed, Jan 06, 2021 at 10:32:42AM +0900, Daejun Park wrote: > In the fast commit, it adds REQ_FUA and REQ_PREFLUSH on each fast commit > block when barrier is enabled. However, in recovery phase, ext4 compares > CRC value in the tail. So it is sufficient adds REQ_FUA and REQ_PREFLUSH > on the block that has tail. Just out of curiosity, how does the new fastcommit code handle tests like generic/475 that simulate sudden disk failure? --D > Signed-off-by: Daejun Park <daejun7.park@...sung.com> > --- > fs/ext4/fast_commit.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c > index 4fcc21c25e79..e66507be334c 100644 > --- a/fs/ext4/fast_commit.c > +++ b/fs/ext4/fast_commit.c > @@ -604,13 +604,13 @@ void ext4_fc_track_range(handle_t *handle, struct inode *inode, ext4_lblk_t star > trace_ext4_fc_track_range(inode, start, end, ret); > } > > -static void ext4_fc_submit_bh(struct super_block *sb) > +static void ext4_fc_submit_bh(struct super_block *sb, bool is_tail) > { > int write_flags = REQ_SYNC; > struct buffer_head *bh = EXT4_SB(sb)->s_fc_bh; > > - /* TODO: REQ_FUA | REQ_PREFLUSH is unnecessarily expensive. */ > - if (test_opt(sb, BARRIER)) > + /* Add REQ_FUA | REQ_PREFLUSH only its tail */ > + if (test_opt(sb, BARRIER) && is_tail) > write_flags |= REQ_FUA | REQ_PREFLUSH; > lock_buffer(bh); > set_buffer_dirty(bh); > @@ -684,7 +684,7 @@ static u8 *ext4_fc_reserve_space(struct super_block *sb, int len, u32 *crc) > *crc = ext4_chksum(sbi, *crc, tl, sizeof(*tl)); > if (pad_len > 0) > ext4_fc_memzero(sb, tl + 1, pad_len, crc); > - ext4_fc_submit_bh(sb); > + ext4_fc_submit_bh(sb, false); > > ret = jbd2_fc_get_buf(EXT4_SB(sb)->s_journal, &bh); > if (ret) > @@ -741,7 +741,7 @@ static int ext4_fc_write_tail(struct super_block *sb, u32 crc) > tail.fc_crc = cpu_to_le32(crc); > ext4_fc_memcpy(sb, dst, &tail.fc_crc, sizeof(tail.fc_crc), NULL); > > - ext4_fc_submit_bh(sb); > + ext4_fc_submit_bh(sb, true); > > return 0; > } > -- > 2.25.1 >
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