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.
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'.
projects / mirror_ubuntu-bionic-kernel.git / commitdiff