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

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On 2019/7/12 19:54, Andreas Gruenbacher wrote:
> On Fri, 12 Jul 2019 at 11:31, Chao Yu <yuchao0@xxxxxxxxxx> 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);
>>>
> .
> 



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