On 2019/7/1 14:40, Chao Yu wrote:
> Hi Xiang,
>
> On 2019/6/29 17:34, Gao Xiang wrote:
>> Hi Chao,
>>
>> On 2019/6/29 15:30, Chao Yu wrote:
>>> Some filesystems like erofs/reiserfs have the ability to pack tail
>>> data into metadata, however iomap framework can only support mapping
>>> inline data with IOMAP_INLINE type, it restricts that:
>>> - inline data should be locating at page #0.
>>> - inline size should equal to .i_size
>>> So we can not use IOMAP_INLINE to handle tail-packing case.
>>>
>>> This patch introduces new mapping type IOMAP_TAIL to map tail-packed
>>> data for further use of erofs.
>>>
>>> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
>>> ---
>>> fs/iomap.c | 22 ++++++++++++++++++++++
>>> include/linux/iomap.h | 1 +
>>> 2 files changed, 23 insertions(+)
>>>
>>> diff --git a/fs/iomap.c b/fs/iomap.c
>>> index 12654c2e78f8..ae7777ce77d0 100644
>>> --- a/fs/iomap.c
>>> +++ b/fs/iomap.c
>>> @@ -280,6 +280,23 @@ iomap_read_inline_data(struct inode *inode, struct page *page,
>>> SetPageUptodate(page);
>>> }
>>>
>>> +static void
>>> +iomap_read_tail_data(struct inode *inode, struct page *page,
>>> + struct iomap *iomap)
>>> +{
>>> + size_t size = i_size_read(inode) & (PAGE_SIZE - 1);
>>> + void *addr;
>>> +
>>> + if (PageUptodate(page))
>>> + return;
>>> +
>>> + addr = kmap_atomic(page);
>>> + memcpy(addr, iomap->inline_data, size);
>>> + memset(addr + size, 0, PAGE_SIZE - size);
>>
>> need flush_dcache_page(page) here for new page cache page since
>> it's generic iomap code (althrough not necessary for x86, arm), I am not sure...
>> see commit d2b2c6dd227b and c01778001a4f...
>
> Thanks for your reminding, these all codes were copied from
> iomap_read_inline_data(), so I think we need a separated patch to fix this issue
> if necessary.
Yes, just a reminder, it is good as it-is.
Thanks,
Gao Xiang
>
> Thanks,
>
>>
>> Thanks,
>> Gao Xiang
>>
>>> + kunmap_atomic(addr);
>>> + SetPageUptodate(page);
>>> +}
>>> +
>>> static loff_t
>>> iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>>> struct iomap *iomap)
>>> @@ -298,6 +315,11 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>>> return PAGE_SIZE;
>>> }
>>>
>>> + if (iomap->type == IOMAP_TAIL) {
>>> + iomap_read_tail_data(inode, page, iomap);
>>> + return PAGE_SIZE;
>>> + }
>>> +
>>> /* zero post-eof blocks as the page may be mapped */
>>> iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
>>> if (plen == 0)
>>> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
>>> index 2103b94cb1bf..7e1ee48e3db7 100644
>>> --- a/include/linux/iomap.h
>>> +++ b/include/linux/iomap.h
>>> @@ -25,6 +25,7 @@ struct vm_fault;
>>> #define IOMAP_MAPPED 0x03 /* blocks allocated at @addr */
>>> #define IOMAP_UNWRITTEN 0x04 /* blocks allocated at @addr in unwritten state */
>>> #define IOMAP_INLINE 0x05 /* data inline in the inode */
>>> +#define IOMAP_TAIL 0x06 /* tail data packed in metdata */
>>>
>>> /*
>>> * Flags for all iomap mappings:
>>>
>> .
>>
