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.
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:
>>
> .
>
