Re: [PATCH v3 14/18] ext4: remove unuseddiscard_partial_page_buffers

[Jan Kara]

On Tue 09-04-13 11:14:23, Lukas Czerner wrote:
> The discard_partial_page_buffers is no longer used anywhere so we can
> simply remove it including the *_no_lock variant and
> EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED define.
> 
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
  Looks good, obviously ;) You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza
> ---
>  fs/ext4/ext4.h  |    8 --
>  fs/ext4/inode.c |  206 -------------------------------------------------------
>  2 files changed, 0 insertions(+), 214 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 2428244..cc9020e 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -593,11 +593,6 @@ enum {
>  #define EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER	0x0020
>  
>  /*
> - * Flags used by ext4_discard_partial_page_buffers
> - */
> -#define EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED	0x0001
> -
> -/*
>   * ioctl commands
>   */
>  #define	EXT4_IOC_GETFLAGS		FS_IOC_GETFLAGS
> @@ -2111,9 +2106,6 @@ extern int ext4_block_zero_page_range(handle_t *handle,
>  		struct address_space *mapping, loff_t from, loff_t length);
>  extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
>  			     loff_t lstart, loff_t lend);
> -extern int ext4_discard_partial_page_buffers(handle_t *handle,
> -		struct address_space *mapping, loff_t from,
> -		loff_t length, int flags);
>  extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
>  extern qsize_t *ext4_get_reserved_space(struct inode *inode);
>  extern void ext4_da_update_reserve_space(struct inode *inode,
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 6003fd1..0d452c1 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -135,9 +135,6 @@ static void ext4_invalidatepage(struct page *page, unsigned int offset,
>  				unsigned int length);
>  static int __ext4_journalled_writepage(struct page *page, unsigned int len);
>  static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh);
> -static int ext4_discard_partial_page_buffers_no_lock(handle_t *handle,
> -		struct inode *inode, struct page *page, loff_t from,
> -		loff_t length, int flags);
>  
>  /*
>   * Test whether an inode is a fast symlink.
> @@ -3352,209 +3349,6 @@ void ext4_set_aops(struct inode *inode)
>  		inode->i_mapping->a_ops = &ext4_aops;
>  }
>  
> -
> -/*
> - * ext4_discard_partial_page_buffers()
> - * Wrapper function for ext4_discard_partial_page_buffers_no_lock.
> - * This function finds and locks the page containing the offset
> - * "from" and passes it to ext4_discard_partial_page_buffers_no_lock.
> - * Calling functions that already have the page locked should call
> - * ext4_discard_partial_page_buffers_no_lock directly.
> - */
> -int ext4_discard_partial_page_buffers(handle_t *handle,
> -		struct address_space *mapping, loff_t from,
> -		loff_t length, int flags)
> -{
> -	struct inode *inode = mapping->host;
> -	struct page *page;
> -	int err = 0;
> -
> -	page = find_or_create_page(mapping, from >> PAGE_CACHE_SHIFT,
> -				   mapping_gfp_mask(mapping) & ~__GFP_FS);
> -	if (!page)
> -		return -ENOMEM;
> -
> -	err = ext4_discard_partial_page_buffers_no_lock(handle, inode, page,
> -		from, length, flags);
> -
> -	unlock_page(page);
> -	page_cache_release(page);
> -	return err;
> -}
> -
> -/*
> - * ext4_discard_partial_page_buffers_no_lock()
> - * Zeros a page range of length 'length' starting from offset 'from'.
> - * Buffer heads that correspond to the block aligned regions of the
> - * zeroed range will be unmapped.  Unblock aligned regions
> - * will have the corresponding buffer head mapped if needed so that
> - * that region of the page can be updated with the partial zero out.
> - *
> - * This function assumes that the page has already been  locked.  The
> - * The range to be discarded must be contained with in the given page.
> - * If the specified range exceeds the end of the page it will be shortened
> - * to the end of the page that corresponds to 'from'.  This function is
> - * appropriate for updating a page and it buffer heads to be unmapped and
> - * zeroed for blocks that have been either released, or are going to be
> - * released.
> - *
> - * handle: The journal handle
> - * inode:  The files inode
> - * page:   A locked page that contains the offset "from"
> - * from:   The starting byte offset (from the beginning of the file)
> - *         to begin discarding
> - * len:    The length of bytes to discard
> - * flags:  Optional flags that may be used:
> - *
> - *         EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED
> - *         Only zero the regions of the page whose buffer heads
> - *         have already been unmapped.  This flag is appropriate
> - *         for updating the contents of a page whose blocks may
> - *         have already been released, and we only want to zero
> - *         out the regions that correspond to those released blocks.
> - *
> - * Returns zero on success or negative on failure.
> - */
> -static int ext4_discard_partial_page_buffers_no_lock(handle_t *handle,
> -		struct inode *inode, struct page *page, loff_t from,
> -		loff_t length, int flags)
> -{
> -	ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT;
> -	unsigned int offset = from & (PAGE_CACHE_SIZE-1);
> -	unsigned int blocksize, max, pos;
> -	ext4_lblk_t iblock;
> -	struct buffer_head *bh;
> -	int err = 0;
> -
> -	blocksize = inode->i_sb->s_blocksize;
> -	max = PAGE_CACHE_SIZE - offset;
> -
> -	if (index != page->index)
> -		return -EINVAL;
> -
> -	/*
> -	 * correct length if it does not fall between
> -	 * 'from' and the end of the page
> -	 */
> -	if (length > max || length < 0)
> -		length = max;
> -
> -	iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
> -
> -	if (!page_has_buffers(page))
> -		create_empty_buffers(page, blocksize, 0);
> -
> -	/* Find the buffer that contains "offset" */
> -	bh = page_buffers(page);
> -	pos = blocksize;
> -	while (offset >= pos) {
> -		bh = bh->b_this_page;
> -		iblock++;
> -		pos += blocksize;
> -	}
> -
> -	pos = offset;
> -	while (pos < offset + length) {
> -		unsigned int end_of_block, range_to_discard;
> -
> -		err = 0;
> -
> -		/* The length of space left to zero and unmap */
> -		range_to_discard = offset + length - pos;
> -
> -		/* The length of space until the end of the block */
> -		end_of_block = blocksize - (pos & (blocksize-1));
> -
> -		/*
> -		 * Do not unmap or zero past end of block
> -		 * for this buffer head
> -		 */
> -		if (range_to_discard > end_of_block)
> -			range_to_discard = end_of_block;
> -
> -
> -		/*
> -		 * Skip this buffer head if we are only zeroing unampped
> -		 * regions of the page
> -		 */
> -		if (flags & EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED &&
> -			buffer_mapped(bh))
> -				goto next;
> -
> -		/* If the range is block aligned, unmap */
> -		if (range_to_discard == blocksize) {
> -			clear_buffer_dirty(bh);
> -			bh->b_bdev = NULL;
> -			clear_buffer_mapped(bh);
> -			clear_buffer_req(bh);
> -			clear_buffer_new(bh);
> -			clear_buffer_delay(bh);
> -			clear_buffer_unwritten(bh);
> -			clear_buffer_uptodate(bh);
> -			zero_user(page, pos, range_to_discard);
> -			BUFFER_TRACE(bh, "Buffer discarded");
> -			goto next;
> -		}
> -
> -		/*
> -		 * If this block is not completely contained in the range
> -		 * to be discarded, then it is not going to be released. Because
> -		 * we need to keep this block, we need to make sure this part
> -		 * of the page is uptodate before we modify it by writeing
> -		 * partial zeros on it.
> -		 */
> -		if (!buffer_mapped(bh)) {
> -			/*
> -			 * Buffer head must be mapped before we can read
> -			 * from the block
> -			 */
> -			BUFFER_TRACE(bh, "unmapped");
> -			ext4_get_block(inode, iblock, bh, 0);
> -			/* unmapped? It's a hole - nothing to do */
> -			if (!buffer_mapped(bh)) {
> -				BUFFER_TRACE(bh, "still unmapped");
> -				goto next;
> -			}
> -		}
> -
> -		/* Ok, it's mapped. Make sure it's up-to-date */
> -		if (PageUptodate(page))
> -			set_buffer_uptodate(bh);
> -
> -		if (!buffer_uptodate(bh)) {
> -			err = -EIO;
> -			ll_rw_block(READ, 1, &bh);
> -			wait_on_buffer(bh);
> -			/* Uhhuh. Read error. Complain and punt.*/
> -			if (!buffer_uptodate(bh))
> -				goto next;
> -		}
> -
> -		if (ext4_should_journal_data(inode)) {
> -			BUFFER_TRACE(bh, "get write access");
> -			err = ext4_journal_get_write_access(handle, bh);
> -			if (err)
> -				goto next;
> -		}
> -
> -		zero_user(page, pos, range_to_discard);
> -
> -		err = 0;
> -		if (ext4_should_journal_data(inode)) {
> -			err = ext4_handle_dirty_metadata(handle, inode, bh);
> -		} else
> -			mark_buffer_dirty(bh);
> -
> -		BUFFER_TRACE(bh, "Partial buffer zeroed");
> -next:
> -		bh = bh->b_this_page;
> -		iblock++;
> -		pos += range_to_discard;
> -	}
> -
> -	return err;
> -}
> -
>  /*
>   * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
>   * up to the end of the block which corresponds to `from'.
> -- 
> 1.7.7.6
> 
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-- 
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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