Re: [RFC PATCH] iomap: generalize IOMAP_INLINE to cover tail-packing case

[Chao Yu <yuchao0@huawei.com>]

Ping, Andreas. :P

On 2019/7/15 17:26, Chao Yu wrote:
> On 2019/7/12 19:54, Andreas Gruenbacher wrote:
>> On Fri, 12 Jul 2019 at 11:31, Chao Yu <yuchao0@huawei.com> wrote:
>>> On 2019/7/11 20:28, Andreas Gruenbacher wrote:
>>>> Something along the lines of the attached, broken patch might work in
>>>> the end.
>>>>
>>>> Andreas
>>>>
>>>> ---
>>>>  fs/buffer.c           | 10 ++++--
>>>>  fs/iomap.c            | 74 +++++++++++++++++++++++++++++--------------
>>>>  include/linux/iomap.h |  3 ++
>>>>  3 files changed, 61 insertions(+), 26 deletions(-)
>>>>
>>>> diff --git a/fs/buffer.c b/fs/buffer.c
>>>> index e450c55f6434..8d8668e377ab 100644
>>>> --- a/fs/buffer.c
>>>> +++ b/fs/buffer.c
>>>> @@ -1873,8 +1873,8 @@ void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
>>>>  EXPORT_SYMBOL(page_zero_new_buffers);
>>>>
>>>>  static void
>>>> -iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
>>>> -             struct iomap *iomap)
>>>> +iomap_to_bh(struct inode *inode, struct page *page, sector_t block,
>>>> +             struct buffer_head *bh, struct iomap *iomap)
>>>>  {
>>>>       loff_t offset = block << inode->i_blkbits;
>>>>
>>>> @@ -1924,6 +1924,10 @@ iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
>>>>                               inode->i_blkbits;
>>>>               set_buffer_mapped(bh);
>>>>               break;
>>>> +     case IOMAP_INLINE:
>>>> +             __iomap_read_inline_data(inode, page, iomap);
>>>> +             set_buffer_uptodate(bh);
>>>> +             break;
>>>>       }
>>>>  }
>>>>
>>>> @@ -1969,7 +1973,7 @@ int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
>>>>                               if (err)
>>>>                                       break;
>>>>                       } else {
>>>> -                             iomap_to_bh(inode, block, bh, iomap);
>>>> +                             iomap_to_bh(inode, page, block, bh, iomap);
>>>>                       }
>>>>
>>>>                       if (buffer_new(bh)) {
>>>> diff --git a/fs/iomap.c b/fs/iomap.c
>>>> index 45aa58e837b5..61188e95def2 100644
>>>> --- a/fs/iomap.c
>>>> +++ b/fs/iomap.c
>>>> @@ -260,24 +260,47 @@ struct iomap_readpage_ctx {
>>>>       struct list_head        *pages;
>>>>  };
>>>>
>>>> -static void
>>>> -iomap_read_inline_data(struct inode *inode, struct page *page,
>>>> +#define offset_in_block(offset, inode) \
>>>> +     ((unsigned long)(offset) & (i_blocksize(inode) - 1))
>>>> +
>>>> +static bool
>>>> +inline_data_within_block(struct inode *inode, struct iomap *iomap,
>>>> +             unsigned int size)
>>>> +{
>>>> +     unsigned int off = offset_in_block(iomap->inline_data, inode);
>>>> +
>>>> +     return size <= i_blocksize(inode) - off;
>>>> +}
>>>> +
>>>> +void
>>>> +__iomap_read_inline_data(struct inode *inode, struct page *page,
>>>>               struct iomap *iomap)
>>>>  {
>>>> -     size_t size = i_size_read(inode);
>>>> +     size_t size = offset_in_block(i_size_read(inode), inode);
>>>> +     unsigned int poff = offset_in_page(iomap->offset);
>>>> +     unsigned int bsize = i_blocksize(inode);
>>>>       void *addr;
>>>>
>>>>       if (PageUptodate(page))
>>>>               return;
>>>>
>>>> -     BUG_ON(page->index);
>>>> -     BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data));
>>>> +     BUG_ON(!inline_data_within_block(inode, iomap, size));
>>>>
>>>>       addr = kmap_atomic(page);
>>>> -     memcpy(addr, iomap->inline_data, size);
>>>> -     memset(addr + size, 0, PAGE_SIZE - size);
>>>> +     memcpy(addr + poff, iomap->inline_data, size);
>>>> +     memset(addr + poff + size, 0, bsize - size);
>>>>       kunmap_atomic(addr);
>>>> -     SetPageUptodate(page);
>>>> +}
>>>> +
>>>> +static void
>>>> +iomap_read_inline_data(struct inode *inode, struct page *page,
>>>> +             struct iomap *iomap)
>>>> +{
>>>> +     unsigned int poff = offset_in_page(iomap->offset);
>>>> +     unsigned int bsize = i_blocksize(inode);
>>>> +
>>>> +     __iomap_read_inline_data(inode, page, iomap);
>>>> +     iomap_set_range_uptodate(page, poff, bsize);
>>>>  }
>>>>
>>>>  static loff_t
>>>> @@ -292,11 +315,8 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>>>>       unsigned poff, plen;
>>>>       sector_t sector;
>>>>
>>>> -     if (iomap->type == IOMAP_INLINE) {
>>>> -             WARN_ON_ONCE(pos);
>>>> +     if (iomap->type == IOMAP_INLINE)
>>>>               iomap_read_inline_data(inode, page, iomap);
>>>> -             return PAGE_SIZE;
>>>
>>> Hi Andreas,
>>>
>>> Thanks for your patch.
>>>
>>> In my erofs test case, filled inline data will be zeroed out due to we fallback
>>> to following flow:
>>>
>>>         if (iomap->type != IOMAP_MAPPED || pos >= i_size_read(inode)) {
>>>                 zero_user(page, poff, plen);
>>>
>>> Should we return before this condition check?
>>
>> Yes, probably by returning i_blocksize(inode) after
>> iomap_read_inline_data, but that alone isn't enough to make the patch
> 
> Could you please resend this diff as a new patch with above fix?
> 
>> work completely. This really needs a review from Christoph and careful
>> testing of all the code paths.
> 
> Later, I can do the test on read path.
> 
> Thanks,
> 
>>
>> Andreas
>>
>>> Thanks,
>>>
>>>> -     }
>>>>
>>>>       /* zero post-eof blocks as the page may be mapped */
>>>>       iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
>>>> @@ -637,6 +657,11 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
>>>>       if (PageUptodate(page))
>>>>               return 0;
>>>>
>>>> +     if (iomap->type == IOMAP_INLINE) {
>>>> +             iomap_read_inline_data(inode, page, iomap);
>>>> +             return 0;
>>>> +     }
>>>> +
>>>>       do {
>>>>               iomap_adjust_read_range(inode, iop, &block_start,
>>>>                               block_end - block_start, &poff, &plen);
>>>> @@ -682,9 +707,7 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
>>>>               goto out_no_page;
>>>>       }
>>>>
>>>> -     if (iomap->type == IOMAP_INLINE)
>>>> -             iomap_read_inline_data(inode, page, iomap);
>>>> -     else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
>>>> +     if (iomap->flags & IOMAP_F_BUFFER_HEAD)
>>>>               status = __block_write_begin_int(page, pos, len, NULL, iomap);
>>>>       else
>>>>               status = __iomap_write_begin(inode, pos, len, page, iomap);
>>>> @@ -761,11 +784,11 @@ iomap_write_end_inline(struct inode *inode, struct page *page,
>>>>  {
>>>>       void *addr;
>>>>
>>>> -     WARN_ON_ONCE(!PageUptodate(page));
>>>> -     BUG_ON(pos + copied > PAGE_SIZE - offset_in_page(iomap->inline_data));
>>>> +     BUG_ON(!inline_data_within_block(inode, iomap, pos + copied));
>>>>
>>>>       addr = kmap_atomic(page);
>>>> -     memcpy(iomap->inline_data + pos, addr + pos, copied);
>>>> +     memcpy(iomap->inline_data + offset_in_block(pos, inode),
>>>> +            addr + offset_in_page(pos), copied);
>>>>       kunmap_atomic(addr);
>>>>
>>>>       mark_inode_dirty(inode);
>>>> @@ -1064,7 +1087,7 @@ iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
>>>>               const struct iomap_ops *ops)
>>>>  {
>>>>       unsigned int blocksize = i_blocksize(inode);
>>>> -     unsigned int off = pos & (blocksize - 1);
>>>> +     unsigned int off = offset_in_block(pos, inode);
>>>>
>>>>       /* Block boundary? Nothing to do */
>>>>       if (!off)
>>>> @@ -1772,21 +1795,26 @@ iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
>>>>       struct iov_iter *iter = dio->submit.iter;
>>>>       size_t copied;
>>>>
>>>> -     BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
>>>> +     BUG_ON(!inline_data_within_block(inode, iomap, pos + length));
>>>>
>>>>       if (dio->flags & IOMAP_DIO_WRITE) {
>>>>               loff_t size = inode->i_size;
>>>>
>>>>               if (pos > size)
>>>> -                     memset(iomap->inline_data + size, 0, pos - size);
>>>> -             copied = copy_from_iter(iomap->inline_data + pos, length, iter);
>>>> +                     memset(iomap->inline_data +
>>>> +                            offset_in_block(size, inode), 0, pos - size);
>>>> +             copied = copy_from_iter(iomap->inline_data +
>>>> +                                     offset_in_block(pos, inode),
>>>> +                                     length, iter);
>>>>               if (copied) {
>>>>                       if (pos + copied > size)
>>>>                               i_size_write(inode, pos + copied);
>>>>                       mark_inode_dirty(inode);
>>>>               }
>>>>       } else {
>>>> -             copied = copy_to_iter(iomap->inline_data + pos, length, iter);
>>>> +             copied = copy_to_iter(iomap->inline_data +
>>>> +                                   offset_in_block(pos, inode),
>>>> +                                   length, iter);
>>>>       }
>>>>       dio->size += copied;
>>>>       return copied;
>>>> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
>>>> index 2103b94cb1bf..a8a60dd2fdc0 100644
>>>> --- a/include/linux/iomap.h
>>>> +++ b/include/linux/iomap.h
>>>> @@ -131,6 +131,9 @@ static inline struct iomap_page *to_iomap_page(struct page *page)
>>>>       return NULL;
>>>>  }
>>>>
>>>> +void __iomap_read_inline_data(struct inode *inode, struct page *page,
>>>> +             struct iomap *iomap);
>>>> +
>>>>  ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
>>>>               const struct iomap_ops *ops);
>>>>  int iomap_readpage(struct page *page, const struct iomap_ops *ops);
>>>>
>> .
>>
> .
>