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Message-ID: <CAHJ8P3LWwA=VzKcr3nXO1uZtkc1H9dmO+5dNy247A2fGn6JHDA@mail.gmail.com>
Date: Thu, 7 Nov 2024 18:53:20 +0800
From: Zhiguo Niu <niuzhiguo84@...il.com>
To: Chao Yu <chao@...nel.org>
Cc: 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
Chao Yu <chao@...nel.org> 于2024年11月7日周四 16:22写道：
>
> On 2024/11/7 14:54, Zhiguo Niu wrote:
> > Chao Yu <chao@...nel.org> 于2024年11月7日周四 14:18写道：
> >>
> >> 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.
> > Hi Chao,
> > OK, thanks for your explaination.
> > btw, Do I need to update a patch about the original issue we disscussed?
> > or you will modify it together?
>
> Zhiguo, let me send a patchset including your patch, now, I'm testing this:
Hi Chao,
It's ok ^^
>
> From c67cb4782a3f1875865f9ae24cce80a59752d600 Mon Sep 17 00:00:00 2001
> From: Chao Yu <chao@...nel.org>
> Date: Thu, 7 Nov 2024 14:52:17 +0800
> Subject: [PATCH] f2fs: fix to requery extent which cross boundary of inquiry
>
> dd if=/dev/zero of=file bs=4k count=5
> 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
>
> There are two problems:
> - continuous extent is split to two
> - FIEMAP_EXTENT_LAST is missing in last extent
>
> The root cause is: if upper boundary of inquiry crosses extent,
> f2fs_map_blocks() will truncate length of returned extent to
> F2FS_BYTES_TO_BLK(len), and also, it will stop to query latter
> extent or hole to make sure current extent is last or not.
>
> In order to fix this issue, once we found an extent locates
> in the end of inquiry range by f2fs_map_blocks(), we need to
> expand inquiry range to requiry.
>
> Reported-by: Zhiguo Niu <zhiguo.niu@...soc.com>
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
> fs/f2fs/data.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 69f1cb0490ee..ee5614324df0 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1896,7 +1896,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> u64 start, u64 len)
> {
> struct f2fs_map_blocks map;
> - sector_t start_blk, last_blk;
> + sector_t start_blk, last_blk, blk_len, max_len;
> pgoff_t next_pgofs;
> u64 logical = 0, phys = 0, size = 0;
> u32 flags = 0;
> @@ -1940,14 +1940,13 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>
> start_blk = F2FS_BYTES_TO_BLK(start);
> last_blk = F2FS_BYTES_TO_BLK(start + len - 1);
> -
> - if (len & F2FS_BLKSIZE_MASK)
> - len = round_up(len, F2FS_BLKSIZE);
> + blk_len = last_blk - start_blk + 1;
> + max_len = F2FS_BYTES_TO_BLK(maxbytes) - start_blk;
>
> next:
> memset(&map, 0, sizeof(map));
> map.m_lblk = start_blk;
> - map.m_len = F2FS_BYTES_TO_BLK(len);
> + map.m_len = blk_len;
> map.m_next_pgofs = &next_pgofs;
> map.m_seg_type = NO_CHECK_TYPE;
>
> @@ -1970,6 +1969,17 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> flags |= FIEMAP_EXTENT_LAST;
> }
>
> + /*
> + * current extent may cross boundary of inquiry, increase len to
> + * requery.
> + */
> + if (!compr_cluster && (map.m_flags & F2FS_MAP_MAPPED) &&
> + map.m_lblk + map.m_len - 1 == last_blk &&
> + blk_len != max_len) {
> + blk_len = max_len;
> + goto next;
> + }
> +
it seems if user input the lenght which is less than the file size,
but return the whole fiemap?
such as:
dd if=/dev/zero of=file bs=4k count=5
xfs_io file -c "fiemap -v 0 16384"
will get extent with lenght = 0x5000? Is this expected?
Or did I understand it wrong?
thanks!
> compr_appended = false;
> /* In a case of compressed cluster, append this to the last extent */
> if (compr_cluster && ((map.m_flags & F2FS_MAP_DELALLOC) ||
> --
> 2.40.1
>
> > thanks!
> >>
> >> 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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