Messages in this thread | | | Date | Sat, 30 Oct 2021 11:02:42 +0800 | Subject | Re: [f2fs-dev] [PATCH] f2fs: skip f2fs_preallocate_blocks() for overwrite case | From | Chao Yu <> |
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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@kernel.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@lists.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%7C421c06812eba4f922b0908d982dcdcc5%7Cf1905eb1c35341c5951662b4a54b5ee6%7C0%7C0%7C637684707374940190%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=u22eEWDAPaAZCyISyjTUOtQDLDuyKxTnNCI3eSwwWro%3D&reserved=0
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