Hi Gu, > -----Original Message----- > From: Gu Zheng [mailto:[email protected]] > Sent: Wednesday, September 03, 2014 5:16 PM > To: [email protected] > Cc: Gu Zheng; [email protected]; > [email protected] > Subject: [f2fs-dev] [PATCH] f2fs: use lock-less list(llist) to simplify the > flush cmd management > > We use flush cmd control to collect many flush cmds, and flush them > together. In this case, we use two list to manage the flush cmds > (collect and dispatch), and one spin lock is used to protect this. > In fact, the lock-less list(llist) is very suitable to this case, > and we use simplify this routine.
Good catch for finding this scenario with llist! > > Signed-off-by: Gu Zheng <[email protected]> > --- > fs/f2fs/f2fs.h | 7 +++---- > fs/f2fs/segment.c | 31 +++++++++---------------------- > 2 files changed, 12 insertions(+), 26 deletions(-) > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index e921242..1dd861c 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -334,16 +334,15 @@ enum { > struct flush_cmd { > struct flush_cmd *next; No needed here, we can remove it. > struct completion wait; > + struct llist_node llnode; > int ret; > }; > > struct flush_cmd_control { > struct task_struct *f2fs_issue_flush; /* flush thread */ > wait_queue_head_t flush_wait_queue; /* waiting queue for wake-up */ > - struct flush_cmd *issue_list; /* list for command issue */ > - struct flush_cmd *dispatch_list; /* list for command dispatch */ > - spinlock_t issue_lock; /* for issue list lock */ > - struct flush_cmd *issue_tail; /* list tail of issue list */ > + struct llist_head issue_list; /* list for command issue */ > + struct llist_node *dispatch_list; /* list for command dispatch */ > }; > > struct f2fs_sm_info { > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index 0aa337c..2db1f95 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -205,24 +205,19 @@ repeat: > if (kthread_should_stop()) > return 0; > > - spin_lock(&fcc->issue_lock); > - if (fcc->issue_list) { > - fcc->dispatch_list = fcc->issue_list; > - fcc->issue_list = fcc->issue_tail = NULL; > - } > - spin_unlock(&fcc->issue_lock); > - > - if (fcc->dispatch_list) { > + if (!llist_empty(&fcc->issue_list)) { > struct bio *bio = bio_alloc(GFP_NOIO, 0); > - struct flush_cmd *cmd, *next; > + struct flush_cmd *cmd; > int ret; > > + fcc->dispatch_list = llist_del_all(&fcc->issue_list); > + fcc->dispatch_list = llist_reverse_order(fcc->dispatch_list); > + > bio->bi_bdev = sbi->sb->s_bdev; > ret = submit_bio_wait(WRITE_FLUSH, bio); > > - for (cmd = fcc->dispatch_list; cmd; cmd = next) { > + llist_for_each_entry(cmd, fcc->dispatch_list, llnode) { Please use llist_for_each_entry_safe, Otherwise we might encounter oops as below: [18727.381582] Call Trace: [18727.381613] [<c107c0bf>] __wake_up_locked+0x1f/0x30 [18727.381626] [<c107c886>] complete+0x36/0x50 [18727.381645] [<f0a01313>] issue_flush_thread+0x93/0x140 [f2fs] [18727.381658] [<c107c530>] ? add_wait_queue+0x50/0x50 [18727.381672] [<f0a01280>] ? add_sit_entry+0xc0/0xc0 [f2fs] [18727.381687] [<c105fabb>] kthread+0x9b/0xb0 [18727.381701] [<c159ad81>] ret_from_kernel_thread+0x21/0x30 [18727.381714] [<c105fa20>] ? flush_kthread_worker+0x80/0x80 Thanks, Yu > cmd->ret = ret; > - next = cmd->next; > complete(&cmd->wait); > } > bio_put(bio); > @@ -230,7 +225,7 @@ repeat: > } > > wait_event_interruptible(*q, > - kthread_should_stop() || fcc->issue_list); > + kthread_should_stop() || !llist_empty(&fcc->issue_list)); > goto repeat; > } > > @@ -249,17 +244,10 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi) > return blkdev_issue_flush(sbi->sb->s_bdev, GFP_KERNEL, NULL); > > init_completion(&cmd.wait); > - cmd.next = NULL; > > - spin_lock(&fcc->issue_lock); > - if (fcc->issue_list) > - fcc->issue_tail->next = &cmd; > - else > - fcc->issue_list = &cmd; > - fcc->issue_tail = &cmd; > - spin_unlock(&fcc->issue_lock); > + llist_add(&cmd.llnode, &fcc->issue_list); > > - if (!fcc->dispatch_list) > + if (fcc->dispatch_list == NULL) > wake_up(&fcc->flush_wait_queue); > > wait_for_completion(&cmd.wait); > @@ -276,7 +264,6 @@ int create_flush_cmd_control(struct f2fs_sb_info *sbi) > fcc = kzalloc(sizeof(struct flush_cmd_control), GFP_KERNEL); > if (!fcc) > return -ENOMEM; > - spin_lock_init(&fcc->issue_lock); > init_waitqueue_head(&fcc->flush_wait_queue); > SM_I(sbi)->cmd_control_info = fcc; > fcc->f2fs_issue_flush = kthread_run(issue_flush_thread, sbi, > -- > 1.7.7 > > > ------------------------------------------------------------------------------ > Slashdot TV. > Video for Nerds. Stuff that matters. > http://tv.slashdot.org/ > _______________________________________________ > Linux-f2fs-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
