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Message-ID: <d5ef36a3-1bcb-40a0-a963-c6d1887c4e4e@kernel.org> Date: Thu, 7 Nov 2024 14:18:10 +0800 From: Chao Yu <chao@...nel.org> To: Zhiguo Niu <niuzhiguo84@...il.com> Cc: Chao Yu <chao@...nel.org>, Zhiguo Niu <zhiguo.niu@...soc.com>, jaegeuk@...nel.org, linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, ke.wang@...soc.com, Hao_hao.Wang@...soc.com Subject: Re: [PATCH V2] f2fs: fix to adjust appropriate length for fiemap On 2024/11/6 16:41, Zhiguo Niu wrote: > Chao Yu <chao@...nel.org> 于2024年11月6日周三 15:40写道： >> >> On 2024/11/6 14:08, Zhiguo Niu wrote: >>> Chao Yu <chao@...nel.org> 于2024年11月6日周三 10:40写道： >>>> >>>> On 2024/11/6 10:26, Zhiguo Niu wrote: >>>>> Chao Yu <chao@...nel.org> 于2024年11月6日周三 10:16写道： >>>>>> >>>>>> On 2024/11/5 19:02, Zhiguo Niu wrote: >>>>>>> Chao Yu <chao@...nel.org> 于2024年11月5日周二 18:39写道： >>>>>>>> >>>>>>>> On 2024/11/5 15:28, Zhiguo Niu wrote: >>>>>>>>> Chao Yu <chao@...nel.org> 于2024年11月5日周二 15:04写道： >>>>>>>>>> >>>>>>>>>> On 2024/11/4 9:56, Zhiguo Niu wrote: >>>>>>>>>>> If user give a file size as "length" parameter for fiemap >>>>>>>>>>> operations, but if this size is non-block size aligned, >>>>>>>>>>> it will show 2 segments fiemap results even this whole file >>>>>>>>>>> is contiguous on disk, such as the following results: >>>>>>>>>>> >>>>>>>>>>> ./f2fs_io fiemap 0 19034 ylog/analyzer.py >>>>>>>>>>> Fiemap: offset = 0 len = 19034 >>>>>>>>>>> logical addr. physical addr. length flags >>>>>>>>>>> 0 0000000000000000 0000000020baa000 0000000000004000 00001000 >>>>>>>>>>> 1 0000000000004000 0000000020bae000 0000000000001000 00001001 >>>>>>>>>>> >>>>>>>>>>> after this patch: >>>>>>>>>>> ./f2fs_io fiemap 0 19034 ylog/analyzer.py >>>>>>>>>>> Fiemap: offset = 0 len = 19034 >>>>>>>>>>> logical addr. physical addr. length flags >>>>>>>>>>> 0 0000000000000000 00000000315f3000 0000000000005000 00001001 >>>>>>>>>>> >>>>>>>>>>> Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com> >>>>>>>>>>> --- >>>>>>>>>>> V2: correct commit msg according to Chao's questions >>>>>>>>>>> f2fs_io has been modified for testing, the length for fiemap is >>>>>>>>>>> real file size, not block number >>>>>>>>>>> --- >>>>>>>>>>> fs/f2fs/data.c | 4 ++-- >>>>>>>>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>>>>>>>> >>>>>>>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>>>>>>>>>> index 306b86b0..9fc229d 100644 >>>>>>>>>>> --- a/fs/f2fs/data.c >>>>>>>>>>> +++ b/fs/f2fs/data.c >>>>>>>>>>> @@ -1966,8 +1966,8 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, >>>>>>>>>>> goto out; >>>>>>>>>>> } >>>>>>>>>>> >>>>>>>>>>> - if (bytes_to_blks(inode, len) == 0) >>>>>>>>>>> - len = blks_to_bytes(inode, 1); >>>>>>>>>>> + if (len & (blks_to_bytes(inode, 1) - 1)) >>>>>>>>>>> + len = round_up(len, blks_to_bytes(inode, 1)); >>>>>>>>>> >>>>>>>>>> How do you think of getting rid of above alignment for len? >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> start_blk = bytes_to_blks(inode, start); >>>>>>>>>>> last_blk = bytes_to_blks(inode, start + len - 1); >>>>>>>>>> >>>>>>>>>> And round up end position w/: >>>>>>>>>> >>>>>>>>>> last_blk = bytes_to_blks(inode, round_up(start + len - 1, F2FS_BLKSIZE)); >>>>>>>>> Hi Chao, >>>>>>>>> I think this will change the current code logic >>>>>>>>> ------------- >>>>>>>>> if (start_blk > last_blk) >>>>>>>>> goto out; >>>>>>>>> ------------- >>>>>>>>> for example, a file with size 19006, but the length from the user is 16384. >>>>>>>>> before this modification, last_blk = bytes_to_blks(inode, start + >>>>>>>>> len - 1) = (inode, 16383) = 3 >>>>>>>>> after the first f2fs_map_blocks(). start_blk change to be 4, >>>>>>>>> after the second f2fs_map_blocks(), fiemap_fill_nex_exten will be >>>>>>>>> called to fill user parameter and then >>>>>>>>> will goto out because start_blk > last_blk, then fiemap flow finishes. >>>>>>>>> but after this modification, last_blk will be 4 >>>>>>>>> will do f2fs_map_blocks() until reach the max_file_blocks(inode) >>>>>>>> >>>>>>>> Yes, you're right, however, w/ this patch, it may change last_blk, e.g. >>>>>>>> >>>>>>>> xfs_io file -c "fiemap -v 0 19006" vs xfs_io file -c "fiemap -v 2 19006" >>>>>>>> start_blk and last_blk will be: 0, 4 and 0, 5. >>>>>>> Hi Chao, >>>>>>> yes, but w/o this patch , the original code still has the same situation?? >>>>>>> for example >>>>>>> xfs_io file -c "fiemap -v 0 16384" vs xfs_io file -c "fiemap -v 2 16384" >>>>>>> start_blk and last_blk will be: 0, 3 and 0, 4. >>>>>> >>>>>> For the case "fiemap -v 2 19006", offset is 2, and length is 19006, so last_offset >>>>>> is 19008, and last_blk should be 4 rather than 5, right? >>>>> hi Chao, >>>>> it is right w/o my patch. >>>>>> >>>>>> And for you case, it calculates last_blk correctly. >>>>> So you suggest that "Should we round_up len after start_blk & last_blk >>>>> calculation?" >>>> >>>> Zhiguo, >>>> >>>> Yes, I think alignment of len should not affect calculation of last_blk. >>>> >>>> I mean this, >>>> >>>> --- >>>> fs/f2fs/data.c | 6 +++--- >>>> include/linux/f2fs_fs.h | 3 ++- >>>> 2 files changed, 5 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>>> index 7d1bb9518a40..cbbb956f420d 100644 >>>> --- a/fs/f2fs/data.c >>>> +++ b/fs/f2fs/data.c >>>> @@ -1967,12 +1967,12 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, >>>> goto out; >>>> } >>>> >>>> - if (bytes_to_blks(inode, len) == 0) >>>> - len = blks_to_bytes(inode, 1); >>>> - >>>> start_blk = bytes_to_blks(inode, start); >>>> last_blk = bytes_to_blks(inode, start + len - 1); >>>> >>>> + if (len & F2FS_BLKSIZE_MASK) >>>> + len = round_up(len, F2FS_BLKSIZE); >>>> + >>> Hi Chao, >>> this verion verify pass with my test case. >>> >>> but there is still another issue in orginal code: >>> ylog/analyzer.py size = 19034 >>> if I input the following cmd(start/length are both real size, not block number) >>> /f2fs_io fiemap 2 16384 ylog/analyzer.py >>> and the results shows: >>> Fiemap: offset = 2 len = 16384 >>> logical addr. physical addr. length flags >>> 0 0000000000000000 0000000e2ebca000 0000000000004000 00001000 >>> 1 0000000000004000 0000000e2ebce000 0000000000001000 00001001 >>> so start_blk/last_blk should be calculate it in the following way? >> >> IIUC, the root cause is f2fs_map_blocks() will truncate size of >> returned extent to F2FS_BYTES_TO_BLK(len), so whenever parameter >> @len doesn't cover last extent, it triggers this bug. >> >> next: >> memset(&map, 0, sizeof(map)); >> map.m_lblk = start_blk; >> map.m_len = F2FS_BYTES_TO_BLK(len); --- limit max size of extent it founds > yes, I think so too. >> map.m_next_pgofs = &next_pgofs; >> map.m_seg_type = NO_CHECK_TYPE; >> ... >> ret = f2fs_map_blocks(inode, &map, F2FS_GET_BLOCK_FIEMAP); >> >> xfs_io file -c "fiemap -v 2 16384" >> file: >> EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS >> 0: [0..31]: 139272..139303 32 0x1000 >> 1: [32..39]: 139304..139311 8 0x1001 >> xfs_io file -c "fiemap -v 0 16384" >> file: >> EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS >> 0: [0..31]: 139272..139303 32 0x1000 >> xfs_io file -c "fiemap -v 0 16385" >> file: >> EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS >> 0: [0..39]: 139272..139311 40 0x1001 > > But If the correct last_blk is calculated correctly, fiemap can be > ended as soon as possible? so the results shown is also right? Zhiguo, IMO, it's not, due to 1) if the extent is last one, FIEMAP_EXTENT_LAST must be tagged to notice user that it doesn't need further fiemap on latter LBA, 2) one continuous extent should not be split to two. Let me figure out a fix for that. Thanks, > such as this special case "xfs_io file -c "fiemap -v 2 16384" we discussed. > but it is fine for me to keep the current codes. > thanks! >> >> Thoughts? >> >> Thanks, >> >>> before: >>> start_blk = bytes_to_blks(inode, start); >>> last_blk = bytes_to_blks(inode, start + len - 1); >>> after: >>> >>> start_blk = bytes_to_blks(inode, start); >>> last_blk = start_blk + bytes_to_blks(inode, len - 1); >>> thanks! >>>> next: >>>> memset(&map, 0, sizeof(map)); >>>> map.m_lblk = start_blk; >>>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h >>>> index b0b821edfd97..954e8e8344b7 100644 >>>> --- a/include/linux/f2fs_fs.h >>>> +++ b/include/linux/f2fs_fs.h >>>> @@ -24,10 +24,11 @@ >>>> #define NEW_ADDR ((block_t)-1) /* used as block_t addresses */ >>>> #define COMPRESS_ADDR ((block_t)-2) /* used as compressed data flag */ >>>> >>>> +#define F2FS_BLKSIZE_MASK (F2FS_BLKSIZE - 1) >>>> #define F2FS_BYTES_TO_BLK(bytes) ((bytes) >> F2FS_BLKSIZE_BITS) >>>> #define F2FS_BLK_TO_BYTES(blk) ((blk) << F2FS_BLKSIZE_BITS) >>>> #define F2FS_BLK_END_BYTES(blk) (F2FS_BLK_TO_BYTES(blk + 1) - 1) >>>> -#define F2FS_BLK_ALIGN(x) (F2FS_BYTES_TO_BLK((x) + F2FS_BLKSIZE - 1)) >>>> +#define F2FS_BLK_ALIGN(x) (F2FS_BYTES_TO_BLK((x) + F2FS_BLKSIZE - 1)) >>>> >>>> /* 0, 1(node nid), 2(meta nid) are reserved node id */ >>>> #define F2FS_RESERVED_NODE_NUM 3 >>>> -- >>>> 2.40.1 >>>> >>>> >>>> >>>>> Thanks >>>>>> >>>>>> Thanks, >>>>>> >>>>>>> but overall last_blk will change loop counts but has not affect on the results. >>>>>>>> >>>>>>>> Should we round_up len after start_blk & last_blk calculation? >>>>>>> I thinks it is ok ,but just a little bit redundant with the following >>>>>>> handling about len. >>>>>>> >>>>>>> if (bytes_to_blks(inode, len) == 0) >>>>>>> len = blks_to_bytes(inode, 1); >>>>>>> >>>>>>> Based on the above situation, >>>>>>> do you have any other good suggestions? ^^ >>>>>>> thanks! >>>>>>> >>>>>>>> >>>>>>>> Thanks, >>>>>>>> >>>>>>>>> thanks！ >>>>>>>>>> >>>>>>>>>> Thanks, >>>>>>>>>> >>>>>>>> >>>>>> >>>> >>
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