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Message-ID: <e2e61445-c1fd-4b88-8402-b9f83111e05e@kernel.org>
Date: Fri, 8 Nov 2024 09:22:00 +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 2024/11/7 18:53, Zhiguo Niu wrote:
> 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?
It's fine?
Quoted from Documentation/filesystems/fiemap.rst
"fm_start, and fm_length specify the logical range within the file
which the process would like mappings for. Extents returned mirror
those on disk - that is, the logical offset of the 1st returned extent
may start before fm_start, and the range covered by the last returned
extent may end after fm_length. All offsets and lengths are in bytes."
Quoted from reply of Darrick:
https://lore.kernel.org/fstests/20210224165057.GB7269@magnolia/
Thanks,
> 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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