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Date: Sun, 12 Dec 2021 11:57:38 +0800 From: Chao Yu <chao@...nel.org> To: Jaegeuk Kim <jaegeuk@...nel.org> Cc: linux-kernel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net Subject: Re: [f2fs-dev] [PATCH] f2fs: skip f2fs_preallocate_blocks() for overwrite case Ping, On 2021/10/30 11:02, Chao Yu wrote: > On 2021/10/30 1:43, Jaegeuk Kim wrote: >> On 10/29, Chao Yu wrote: >>> Ping, >>> >>> On 2021/9/29 8:05, Chao Yu wrote: >>>> On 2021/9/29 3:08, Jaegeuk Kim wrote: >>>>> On 09/28, Chao Yu wrote: >>>>>> In f2fs_file_write_iter(), let's use f2fs_overwrite_io() to >>>>>> check whethere it is overwrite case, for such case, we can skip >>>>>> f2fs_preallocate_blocks() in order to avoid f2fs_do_map_lock(), >>>>>> which may be blocked by checkpoint() potentially. >>>>>> >>>>>> Signed-off-by: Chao Yu <chao@...nel.org> >>>>>> --- >>>>>> fs/f2fs/file.c | 4 ++++ >>>>>> 1 file changed, 4 insertions(+) >>>>>> >>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>>>> index 13deae03df06..51fecb2f4db5 100644 >>>>>> --- a/fs/f2fs/file.c >>>>>> +++ b/fs/f2fs/file.c >>>>>> @@ -4321,6 +4321,10 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from) >>>>>> preallocated = true; >>>>>> target_size = iocb->ki_pos + iov_iter_count(from); >>>>>> + if (f2fs_overwrite_io(inode, iocb->ki_pos, >>>>>> + iov_iter_count(from))) >>>>>> + goto write; >>>>> >>>>> This calls f2fs_map_blocks() which can be duplicate, if it's not the overwirte >>>>> case. Do we have other benefit? >>>> >>>> f2fs_overwrite_io() will break for append write case w/ below check: >>>> >>>> if (pos + len > i_size_read(inode)) >>>> return false; >>>> >>>> I guess we may only suffer double f2fs_map_blocks() for write hole >>>> case, e.g. truncate to large size & write inside the filesize. For >>>> this case, how about adding a condition to allow double f2fs_map_blocks() >>>> only if write size is smaller than a threshold? >> >> I still don't see the benefit much to do double f2fs_map_blocks. What is the >> problem here? > > There is potential hangtask happened during swapfile's writeback: > > - loop_kthread_worker_fn > - kthread_worker_fn > - loop_queue_work > - lo_rw_aio > - f2fs_file_write_iter > - f2fs_preallocate_blocks > - f2fs_map_blocks > - down_read > - rwsem_down_read_slowpath > - schedule > > I try to mitigate such issue by preallocating swapfile's block address and > avoid f2fs_do_map_lock() as much as possible in swapfile's writeback path... > > Thanks, > >> >>>> >>>> Thanks, >>>> >>>>> >>>>>> + >>>>>> err = f2fs_preallocate_blocks(iocb, from); >>>>>> if (err) { >>>>>> out_err: >>>>>> -- >>>>>> 2.32.0 >>>> >>>> >>>> _______________________________________________ >>>> Linux-f2fs-devel mailing list >>>> Linux-f2fs-devel@...ts.sourceforge.net >>>> https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.sourceforge.net%2Flists%2Flistinfo%2Flinux-f2fs-devel&data=04%7C01%7Cchao.yu%40oppo.com%7Cbb41006c3f6d4e4d600a08d99b51cbcd%7Cf1905eb1c35341c5951662b4a54b5ee6%7C0%7C0%7C637711597895400286%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=%2BlEAXWLpV5wGX2hL0Wj5p2qX0AqfUFI05Qiqdp8PK8g%3D&reserved=0 > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@...ts.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
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