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Date: Mon, 1 Nov 2021 15:12:57 +0800 From: Chao Yu <chao@...nel.org> To: Hyeong-Jun Kim <hj514.kim@...sung.com>, Jaegeuk Kim <jaegeuk@...nel.org> Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org Subject: Re: [PATCH] F2FS: invalidate META_MAPPING before IPU/DIO write 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 (b) write new data to blk 0x200 using IPU or DIO, but outdated data 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? 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@...sung.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))) >>> >> >> >
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