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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mlVLEIno; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mlVLEIno" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E774A1F000E9; Thu, 20 Aug 2026 05:09:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787202573; bh=N24Y3yVF3+EQwVjjX0B1bszJonbliAYAlb9tYFuVdXM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=mlVLEInoUyVuTJ3oF0nbCaISxgFRmZvr9Z82JrKikQlanXy7F86wu0DFuyBx61TPS bpfybHZI8GA5ou9gapUMibEoc7e2YCWFVZn79Ry3fnV2piDQk8dGFE9jm0lId9dEFx xlpIcIjrVtcAoYlS41LDRqGDvdo1P/cZXOfNRq2Eef8s0wZn1TnuN7JWZxu6Q7aTKC 3MEIcFRZr09YlGemM8yX3kJp8TXzAT8f3QhWOss/NcgzINTaC7gPvoZ/KrDv2kHJOz 9B2OFZRyIe9FgcW+BvVI97E2Xwu1uMqAI4pKW7Za6DgSm7Ksvvqfed/xuDWC8ZYKNg ns/e1ykCA8G7A== Date: Thu, 20 Aug 2026 05:09:31 +0000 From: Jaegeuk Kim To: Chao Yu Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [f2fs-dev] [PATCH v1 04/12] f2fs: cache: introduce writeback thread Message-ID: References: <20260820031721.12218-1-chao@kernel.org> <20260820031721.12218-5-chao@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260820031721.12218-5-chao@kernel.org> On 08/20, Chao Yu via Linux-f2fs-devel wrote: > This patch introduces a background writeback kthread (f2fs_writeback-x:y) > to periodically flush dirty metadata cache entries with a default > interval of 5 seconds. > > It manages thread lifecycle across mount, unmount, and remount (rw/ro) > transitions, and hooks synchronous flushing into checkpoint commits. > > Signed-off-by: Chao Yu > --- > fs/f2fs/cache.c | 54 ++++++++++++++++++++++++++++++++++++++++++++ > fs/f2fs/cache.h | 13 +++++++++++ > fs/f2fs/checkpoint.c | 1 + > fs/f2fs/f2fs.h | 3 +++ > fs/f2fs/super.c | 31 ++++++++++++++++++++++++- > 5 files changed, 101 insertions(+), 1 deletion(-) > > diff --git a/fs/f2fs/cache.c b/fs/f2fs/cache.c > index c071364822c4..cb5b26046162 100644 > --- a/fs/f2fs/cache.c > +++ b/fs/f2fs/cache.c > @@ -611,3 +611,57 @@ unsigned long f2fs_shrink_cache(struct f2fs_sb_info *sbi, > { > return f2fs_do_shrink_cache(META_CACHE(sbi), nr_to_scan); > } > + > +static int f2fs_cache_writeback_kthread(void *data) > +{ > + struct f2fs_sb_info *sbi = data; > + struct f2fs_cache_kthread *cache_thread = &sbi->cache_thread; > + wait_queue_head_t *wq = &cache_thread->cache_wb_wq; > + unsigned int interval = DEF_DIRTY_CACHE_TIMEOUT; > + > + set_freezable(); > + > + while (!kthread_should_stop()) { > + wait_event_freezable_timeout(*wq, > + kthread_should_stop() || > + cache_thread->cache_wb_task == NULL, > + msecs_to_jiffies(interval)); > + > + if (kthread_should_stop()) > + break; > + if (f2fs_cp_error(sbi)) > + continue; > + } > + return 0; > +} > + > +int f2fs_start_cache_wb_thread(struct f2fs_sb_info *sbi) > +{ > + struct f2fs_cache_kthread *cache_thread = &sbi->cache_thread; > + dev_t dev = sbi->sb->s_dev; > + char name[36]; > + > + if (cache_thread->cache_wb_task) > + return 0; > + > + init_waitqueue_head(&cache_thread->cache_wb_wq); > + snprintf(name, sizeof(name), "f2fs_writeback-%u:%u", > + MAJOR(dev), MINOR(dev)); > + > + cache_thread->cache_wb_task = kthread_run(f2fs_cache_writeback_kthread, > + sbi, "%s", name); > + if (IS_ERR(cache_thread->cache_wb_task)) > + return PTR_ERR(cache_thread->cache_wb_task); > + return 0; > +} > + > +void f2fs_stop_cache_wb_thread(struct f2fs_sb_info *sbi) > +{ > + struct f2fs_cache_kthread *cache_thread = &sbi->cache_thread; > + > + if (!cache_thread->cache_wb_task) > + return; > + > + kthread_stop(cache_thread->cache_wb_task); > + cache_thread->cache_wb_task = NULL; > +} > diff --git a/fs/f2fs/cache.h b/fs/f2fs/cache.h > index d92b6f3ed585..5e9fe8c0b15c 100644 > --- a/fs/f2fs/cache.h > +++ b/fs/f2fs/cache.h > @@ -191,4 +191,17 @@ void f2fs_stop_cache_wb_thread(struct f2fs_sb_info *sbi); > unsigned long f2fs_shrink_cache(struct f2fs_sb_info *sbi, > unsigned long nr_to_scan); > > +#define DEF_DIRTY_CACHE_TIMEOUT 5000 > + > +struct f2fs_cache_kthread { > + struct task_struct *cache_wb_task; > + wait_queue_head_t cache_wb_wq; > + atomic_t cache_wb_trigger; > + unsigned int cache_wb_interval_ms; > +}; > + > +int f2fs_start_cache_wb_thread(struct f2fs_sb_info *sbi); > +void f2fs_stop_cache_wb_thread(struct f2fs_sb_info *sbi); > +void f2fs_sync_cache_wb(struct f2fs_sb_info *sbi); > + > #endif /* _LINUX_F2FS_CACHE_H */ > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c > index f81ba8cc861a..729d19680caf 100644 > --- a/fs/f2fs/checkpoint.c > +++ b/fs/f2fs/checkpoint.c > @@ -1596,6 +1596,7 @@ static int block_operations(struct f2fs_sb_info *sbi) > * sbi->node_change is used only for AIO write_begin path which produces > * dirty node blocks and some checkpoint values by block allocation. > */ > + Unnecessary line. > __prepare_cp_block(sbi); > f2fs_up_write(&sbi->node_change); > return err; > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index 9b7c60bbb137..6e20b3586f26 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -2108,6 +2108,9 @@ struct f2fs_sb_info { > > /* f2fs internal cache */ > struct f2fs_cached_block_list meta_blocks; > + > + /* internal cache flush thread */ > + struct f2fs_cache_kthread cache_thread; > }; > > /* Definitions to access f2fs_sb_info */ > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c > index bcfb1f97850e..89affe72f4fc 100644 > --- a/fs/f2fs/super.c > +++ b/fs/f2fs/super.c > @@ -1998,6 +1998,7 @@ static void f2fs_put_super(struct super_block *sb) > * flush all issued checkpoints and stop checkpoint issue thread. > * after then, all checkpoints should be done by each process context. > */ > + f2fs_stop_cache_wb_thread(sbi); > f2fs_stop_ckpt_thread(sbi); > > /* > @@ -2799,6 +2800,7 @@ static int __f2fs_remount(struct fs_context *fc, struct super_block *sb) > unsigned int flags = fc->sb_flags; > int err; > bool need_restart_gc = false, need_stop_gc = false; > + bool need_restart_wb = false, need_stop_wb = false; > bool need_restart_flush = false, need_stop_flush = false; > bool need_restart_discard = false, need_stop_discard = false; > bool need_enable_checkpoint = false, need_disable_checkpoint = false; > @@ -2957,6 +2959,18 @@ static int __f2fs_remount(struct fs_context *fc, struct super_block *sb) > need_stop_gc = true; > } > > + if (flags & SB_RDONLY) { > + if (sbi->cache_thread.cache_wb_task) { > + f2fs_stop_cache_wb_thread(sbi); > + need_restart_wb = true; > + } > + } else if (!sbi->cache_thread.cache_wb_task) { > + err = f2fs_start_cache_wb_thread(sbi); > + if (err) > + goto restore_gc; > + need_stop_wb = true; > + } > + > if (flags & SB_RDONLY) { > sync_inodes_sb(sb); > > @@ -2979,7 +2993,7 @@ static int __f2fs_remount(struct fs_context *fc, struct super_block *sb) > } else { > err = f2fs_create_flush_cmd_control(sbi); > if (err) > - goto restore_gc; > + goto restore_wb; > need_stop_flush = true; > } > > @@ -3075,6 +3089,13 @@ static int __f2fs_remount(struct fs_context *fc, struct super_block *sb) > clear_opt(sbi, FLUSH_MERGE); > f2fs_destroy_flush_cmd_control(sbi, false); > } > +restore_wb: > + if (need_restart_wb) { > + if (f2fs_start_cache_wb_thread(sbi)) > + f2fs_warn(sbi, "background cache writeback thread has stopped"); > + } else if (need_stop_wb) { > + f2fs_stop_cache_wb_thread(sbi); > + } > restore_gc: > if (need_restart_gc) { > if (f2fs_start_gc_thread(sbi)) > @@ -5461,6 +5482,12 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc) > goto sync_free_meta; > } > > + if (!f2fs_readonly(sb)) { > + err = f2fs_start_cache_wb_thread(sbi); > + if (err) > + goto stop_gc_thread; > + } > + > /* recover broken superblock */ > if (recovery) { > err = f2fs_commit_super(sbi, true); > @@ -5483,6 +5510,8 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc) > sbi->umount_lock_holder = NULL; > return 0; > > +stop_gc_thread: > + f2fs_stop_gc_thread(sbi); > sync_free_meta: > /* safe to flush all the data */ > sync_filesystem(sbi->sb); > -- > 2.49.0 > > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel