[RFC PATCH V2 6/6] ext4: reimplement fiemap on delayed extent tree

[Yongqiang Yang <xiaoqiangnk@gmail.com>]

This patch reimplements fiemap on delayed extent tree.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
---
 fs/ext4/extents.c |  186 +++++++----------------------------------------------
 1 files changed, 23 insertions(+), 163 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index bdbb984..c2ae125 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3909,193 +3909,53 @@ static int ext4_ext_fiemap_cb(struct inode *inode, ext4_lblk_t next,
 		       struct ext4_ext_cache *newex, struct ext4_extent *ex,
 		       void *data)
 {
+	struct delayed_extent de;
 	__u64	logical;
 	__u64	physical;
 	__u64	length;
 	__u32	flags = 0;
+	ext4_lblk_t next_del;
 	int		ret = 0;
 	struct fiemap_extent_info *fieinfo = data;
 	unsigned char blksize_bits;
 
-	blksize_bits = inode->i_sb->s_blocksize_bits;
-	logical = (__u64)newex->ec_block << blksize_bits;
+	de.start = newex->ec_block;
+	down_read(&EXT4_I(inode)->i_data_sem);
+	next_del = ext4_de_find_extent(inode, &de);
+	up_read(&EXT4_I(inode)->i_data_sem);
 
+	next = min(next_del, next);
 	if (newex->ec_start == 0) {
 		/*
 		 * No extent in extent-tree contains block @newex->ec_start,
 		 * then the block may stay in 1)a hole or 2)delayed-extent.
-		 *
-		 * Holes or delayed-extents are processed as follows.
-		 * 1. lookup dirty pages with specified range in pagecache.
-		 *    If no page is got, then there is no delayed-extent and
-		 *    return with EXT_CONTINUE.
-		 * 2. find the 1st mapped buffer,
-		 * 3. check if the mapped buffer is both in the request range
-		 *    and a delayed buffer. If not, there is no delayed-extent,
-		 *    then return.
-		 * 4. a delayed-extent is found, the extent will be collected.
 		 */
-		ext4_lblk_t	end = 0;
-		pgoff_t		last_offset;
-		pgoff_t		offset;
-		pgoff_t		index;
-		pgoff_t		start_index = 0;
-		struct page	**pages = NULL;
-		struct buffer_head *bh = NULL;
-		struct buffer_head *head = NULL;
-		unsigned int nr_pages = PAGE_SIZE / sizeof(struct page *);
-
-		pages = kmalloc(PAGE_SIZE, GFP_KERNEL);
-		if (pages == NULL)
-			return -ENOMEM;
-
-		offset = logical >> PAGE_SHIFT;
-repeat:
-		last_offset = offset;
-		head = NULL;
-		ret = find_get_pages_tag(inode->i_mapping, &offset,
-					PAGECACHE_TAG_DIRTY, nr_pages, pages);
-
-		if (!(flags & FIEMAP_EXTENT_DELALLOC)) {
-			/* First time, try to find a mapped buffer. */
-			if (ret == 0) {
-out:
-				for (index = 0; index < ret; index++)
-					page_cache_release(pages[index]);
-				/* just a hole. */
-				kfree(pages);
-				return EXT_CONTINUE;
-			}
-			index = 0;
-
-next_page:
-			/* Try to find the 1st mapped buffer. */
-			end = ((__u64)pages[index]->index << PAGE_SHIFT) >>
-				  blksize_bits;
-			if (!page_has_buffers(pages[index]))
-				goto out;
-			head = page_buffers(pages[index]);
-			if (!head)
-				goto out;
-
-			index++;
-			bh = head;
-			do {
-				if (end >= newex->ec_block +
-					newex->ec_len)
-					/* The buffer is out of
-					 * the request range.
-					 */
-					goto out;
-
-				if (buffer_mapped(bh) &&
-				    end >= newex->ec_block) {
-					start_index = index - 1;
-					/* get the 1st mapped buffer. */
-					goto found_mapped_buffer;
-				}
-
-				bh = bh->b_this_page;
-				end++;
-			} while (bh != head);
-
-			/* No mapped buffer in the range found in this page,
-			 * We need to look up next page.
-			 */
-			if (index >= ret) {
-				/* There is no page left, but we need to limit
-				 * newex->ec_len.
-				 */
-				newex->ec_len = end - newex->ec_block;
-				goto out;
-			}
-			goto next_page;
-		} else {
-			/*Find contiguous delayed buffers. */
-			if (ret > 0 && pages[0]->index == last_offset)
-				head = page_buffers(pages[0]);
-			bh = head;
-			index = 1;
-			start_index = 0;
-		}
-
-found_mapped_buffer:
-		if (bh != NULL && buffer_delay(bh)) {
-			/* 1st or contiguous delayed buffer found. */
-			if (!(flags & FIEMAP_EXTENT_DELALLOC)) {
-				/*
-				 * 1st delayed buffer found, record
-				 * the start of extent.
-				 */
-				flags |= FIEMAP_EXTENT_DELALLOC;
-				newex->ec_block = end;
-				logical = (__u64)end << blksize_bits;
-			}
-			/* Find contiguous delayed buffers. */
-			do {
-				if (!buffer_delay(bh))
-					goto found_delayed_extent;
-				bh = bh->b_this_page;
-				end++;
-			} while (bh != head);
-
-			for (; index < ret; index++) {
-				if (!page_has_buffers(pages[index])) {
-					bh = NULL;
-					break;
-				}
-				head = page_buffers(pages[index]);
-				if (!head) {
-					bh = NULL;
-					break;
-				}
-
-				if (pages[index]->index !=
-				    pages[start_index]->index + index
-				    - start_index) {
-					/* Blocks are not contiguous. */
-					bh = NULL;
-					break;
-				}
-				bh = head;
-				do {
-					if (!buffer_delay(bh))
-						/* Delayed-extent ends. */
-						goto found_delayed_extent;
-					bh = bh->b_this_page;
-					end++;
-				} while (bh != head);
-			}
-		} else if (!(flags & FIEMAP_EXTENT_DELALLOC))
-			/* a hole found. */
-			goto out;
-
-found_delayed_extent:
-		newex->ec_len = min(end - newex->ec_block,
-						(ext4_lblk_t)EXT_INIT_MAX_LEN);
-		if (ret == nr_pages && bh != NULL &&
-			newex->ec_len < EXT_INIT_MAX_LEN &&
-			buffer_delay(bh)) {
-			/* Have not collected an extent and continue. */
-			for (index = 0; index < ret; index++)
-				page_cache_release(pages[index]);
-			goto repeat;
+		if (de.len == 0)
+			/* A hole found. */
+			return EXT_CONTINUE;
+
+		if (de.start > newex->ec_block) {
+			/* A hole found. */
+			newex->ec_len = min(de.start - newex->ec_block,
+					    newex->ec_len);
+			return EXT_CONTINUE;
 		}
 
-		for (index = 0; index < ret; index++)
-			page_cache_release(pages[index]);
-		kfree(pages);
+		flags |= FIEMAP_EXTENT_DELALLOC;
+		newex->ec_len = de.start + de.len - newex->ec_block;
 	}
 
-	physical = (__u64)newex->ec_start << blksize_bits;
-	length =   (__u64)newex->ec_len << blksize_bits;