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s=k20201202; t=1635754270; bh=RUFki9qBrHYRF5mCH4qHIpQeS+hm5cKlVdDUyxWnQk0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=S39LsCj1UWB+6RfF10axT+FEVP8jlyFOoAnhYfqBafnBOaWrvDmaGWXZhNhc8ASW3 qGRdGG8TMGZBlaphRXuBqCShKR/rrD3x1x7Wskg1bGdLND44rTR7FApVpxzQFzDnJJ PKt+Sy41FixjDC6sGjh1FSgBQNZo2lZjmzCf7vUqMKeiRRZwKC1+ev0LoQFjYxnc9P pDMG7h41EpqDPIhL37Va850QIWr0KRqKDAbhkIYgIjQIS6QRFnJkkNrIR0vrPjg6Ox vmSQxU9+IEtVR5NTOT9NonzbFwibWmtZ80u6vfk9puFzW/IP2WDqyVzlALN1Nih7jt NDvNuUh9VFPEQ== Message-ID: Date: Mon, 1 Nov 2021 16:11:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.1 Content-Language: en-US To: Hyeong-Jun Kim , Jaegeuk Kim References: <20211101054214.24456-1-hj514.kim@samsung.com> <9a0360922130485f4252970de4bb535667cc26e9.camel@samsung.com> <75c52307-7bfd-2408-d067-26d1fca7bb73@kernel.org> <02ffe8465f514102f5278e97bf3854c520fae91d.camel@samsung.com> From: Chao Yu In-Reply-To: <02ffe8465f514102f5278e97bf3854c520fae91d.camel@samsung.com> X-Headers-End: 1mhSPT-0002fK-JA Subject: Re: [f2fs-dev] [PATCH] F2FS: invalidate META_MAPPING before IPU/DIO write X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2021/11/1 15:23, Hyeong-Jun Kim wrote: > On Mon, 2021-11-01 at 15:12 +0800, Chao Yu wrote: >> On 2021/11/1 15:09, Hyeong-Jun Kim wrote: >>> On Mon, 2021-11-01 at 14:28 +0800, Chao Yu wrote: >>>> On 2021/11/1 13:42, Hyeong-Jun Kim wrote: >>>>> Encrypted pages during GC are read and cached in META_MAPPING. >>>>> However, due to cached pages in META_MAPPING, there is an issue >>>>> where >>>>> newly written pages are lost by IPU or DIO writes. >>>>> >>>>> Thread A Thread B >>>>> - f2fs_gc(): blk 0x10 -> 0x20 (a) >>>>> - IPU or DIO write on >>>>> blk >>>>> 0x20 (b) >>>>> - f2fs_gc(): blk 0x20 -> 0x30 (c) >>>>> >>>>> (a) page for blk 0x20 is cached in META_MAPPING and page for >>>>> blk >>>>> 0x10 >>>>> is invalidated from META_MAPPING. >>>>> (b) write new data to blk 0x200 using IPU or DIO, but outdated >>>>> data >>>>> still remains in META_MAPPING. >>>>> (c) f2fs_gc() try to move blk from 0x20 to 0x30 using cached >>>>> page >>>>> in >>>>> META_MAPPING. In conclusion, the newly written data in >>>>> (b) is >>>>> lost. >>>> >>>> In c), f2fs_gc() will readahead encrypted block from disk via >>>> ra_data_block() anyway, >>>> not matter cached encrypted page of meta inode is uptodate or >>>> not, so >>>> it's safe, right? >>> >>> Right, >>> However, if DIO write is performed between phase 3 and phase 4 of >>> f2fs_gc(), >>> the cached page of meta_mapping will be out-dated, though it read >>> data >>> from >>> disk via ra_data_block() in phase 3. >>> >>> What do you think? >> >> Due to i_gc_rwsem lock coverage, the race condition should not happen >> right now? >> > - Thread A - Thread B > /* phase 3 */ > down_write(i_gc_rwsem) > ra_data_block() > up_write(i_gc_rwsem) > > f2fs_direct_IO() : > > down_read(i_gc_rwsem) > > __blockdev_direct_IO() > ... > > get_ddata_block_dio_write() > ... > > f2fs_dio_submit_bio() > > up_read(i_gc_rwsem) > /* phase 4 */ > down_write(i_gc_rwsem) > move_data_block() > up_write(i_gc_rwsem) > > It looks, i_gc_rwsem could not protect page update between phase 3 and > 4. > > Am I missing anything? It looks you're right, there is a hole in between readahead and movepage functions... Could you please update the race condition description? and add a tag as below to fix stable kernel as well: Fixes: 6aa58d8ad20a ("f2fs: readahead encrypted block during GC") Thanks, > > Thanks > >> Thanks, >> >>> Thanks, >>>> Am I missing anything? >>>> >>>> Thanks, >>>> >>>>> To address this issue, invalidating pages in META_MAPPING >>>>> before >>>>> IPU or >>>>> DIO write. >>>>> >>>>> Signed-off-by: Hyeong-Jun Kim < >>>>> hj514.kim@samsung.com >>>>> >>>>> >>>>> --- >>>>> fs/f2fs/data.c | 2 ++ >>>>> fs/f2fs/segment.c | 3 +++ >>>>> 2 files changed, 5 insertions(+) >>>>> >>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>>>> index 74e1a350c1d8..9f754aaef558 100644 >>>>> --- a/fs/f2fs/data.c >>>>> +++ b/fs/f2fs/data.c >>>>> @@ -1708,6 +1708,8 @@ int f2fs_map_blocks(struct inode *inode, >>>>> struct f2fs_map_blocks *map, >>>>> */ >>>>> f2fs_wait_on_block_writeback_range(inode, >>>>> map->m_pblk, >>>>> map- >>>>>> m_len); >>>>> >>>>> + invalidate_mapping_pages(META_MAPPING(sbi), >>>>> + map->m_pblk, >>>>> map- >>>>>> m_pblk); >>>>> >>>>> >>>>> if (map->m_multidev_dio) { >>>>> block_t blk_addr = map->m_pblk; >>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >>>>> index 526423fe84ce..f57c55190f9e 100644 >>>>> --- a/fs/f2fs/segment.c >>>>> +++ b/fs/f2fs/segment.c >>>>> @@ -3652,6 +3652,9 @@ int f2fs_inplace_write_data(struct >>>>> f2fs_io_info *fio) >>>>> goto drop_bio; >>>>> } >>>>> >>>>> + invalidate_mapping_pages(META_MAPPING(fio->sbi), >>>>> + fio->new_blkaddr, fio- >>>>>> new_blkaddr); >>>>> + >>>>> stat_inc_inplace_blocks(fio->sbi); >>>>> >>>>> if (fio->bio && !(SM_I(sbi)->ipu_policy & (1 << >>>>> F2FS_IPU_NOCACHE))) >>>>> >>>> >>>> >> >> > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel