From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaegeuk Kim Subject: Re: [PATCH 3/9] f2fs: change retry waiting for f2fs_write_single_data_page() Date: Thu, 27 Jan 2022 17:34:31 -0800 Message-ID: References: <164325106958.29787.4865219843242892726.stgit@noble.brown> <164325158956.29787.7016948342209980097.stgit@noble.brown> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643333674; bh=syJ8YNq0jFqssCN+Fpn6CejIFER0XxHyJW+5cZh7qQA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=r4MmK2L91UnUY3Ju+lob6pGYrfuC4tFQze7/UdZcwtg0my1bI0HYZ/EGzcR2/0eYh 5qWQkXkz6GQ99yyiTKsnnZ4hM95RpS6f7bdJAM5P56admAP3hc/ZCtXKNCnRVkrgES v2zuReXf7omP1BD/F2BPe0mg+8tbNoZzsZhdyhFKiYcIFiKTzLCcaIL+zbZB+jgKI2 HaKelY2L0Vg6ndyDgX/aggsEHmYplzWVSHFk3KYEO4hj0B99GHfDlJ8bPCc2gICQtz XRdKz8lPe2Sew/3rSqRIVIUhmZZ9ob0Va5c0yw/atKn6Dw4IaoROTNoyJVls08WLFV 3jQ5xdJOfRU/w== Content-Disposition: inline In-Reply-To: <164325158956.29787.7016948342209980097.stgit@noble.brown> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: NeilBrown Cc: Andrew Morton , Chao Yu , Jeff Layton , Ilya Dryomov , Miklos Szeredi , Trond Myklebust , Anna Schumaker , Ryusuke Konishi , "Darrick J. Wong" , Philipp Reisner , Lars Ellenberg , Paolo Valente , Jens Axboe , linux-mm@kvack.org, linux-nilfs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-ext4@vger.kernel.org, ceph-devel@vger.kernel.org, drbd-dev@lists.linbit.com, linux-kernel@vger.kern On 01/27, NeilBrown wrote: > f2fs_write_single_data_page() can return -EAGAIN if it cannot get > the cp_rwsem lock - it holds a page lock and so cannot wait for it. > > Some code which calls f2fs_write_single_data_page() use > congestion_wait() and then tries again. congestion_wait() doesn't do > anything useful as congestion is no longer tracked. So this is just a > simple sleep. > > A better approach is it wait until the cp_rwsem lock can be taken - then > try again. There is certainly no point trying again *before* the lock > can be taken. > > Signed-off-by: NeilBrown > --- > fs/f2fs/compress.c | 6 +++--- > fs/f2fs/data.c | 9 ++++++--- > 2 files changed, 9 insertions(+), 6 deletions(-) > > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c > index d0c3aeba5945..58ff7f4b296c 100644 > --- a/fs/f2fs/compress.c > +++ b/fs/f2fs/compress.c > @@ -1505,9 +1505,9 @@ static int f2fs_write_raw_pages(struct compress_ctx *cc, > if (IS_NOQUOTA(cc->inode)) > return 0; > ret = 0; > - cond_resched(); > - congestion_wait(BLK_RW_ASYNC, > - DEFAULT_IO_TIMEOUT); > + /* Wait until we can get the lock, then try again. */ > + f2fs_lock_op(F2FS_I_SB(cc->inode)); > + f2fs_unlock_op(F2FS_I_SB(cc->inode)); Since checkpoint uses down_write(cp_rwsem), I'm not sure the write path is safe and needs to wait for checkpoint. Can we just do io_schedule_timeout()? > goto retry_write; > } > return ret; > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > index 8c417864c66a..1d2341163e2c 100644 > --- a/fs/f2fs/data.c > +++ b/fs/f2fs/data.c > @@ -3047,9 +3047,12 @@ static int f2fs_write_cache_pages(struct address_space *mapping, > } else if (ret == -EAGAIN) { > ret = 0; > if (wbc->sync_mode == WB_SYNC_ALL) { > - cond_resched(); > - congestion_wait(BLK_RW_ASYNC, > - DEFAULT_IO_TIMEOUT); > + /* Wait until we can get the > + * lock, then try again. > + */ > + f2fs_lock_op(F2FS_I_SB(mapping->host)); > + f2fs_unlock_op(F2FS_I_SB(mapping->host)); > + > goto retry_write; > } > goto next; >