Re: [PATCH V20 02/19] Btrfs: subpage-blocksize: Fix whole page write

For the subpage-blocksize scenario, a page can contain multiple
blocks. In such cases, this patch handles writing data to files.

Also, When setting EXTENT_DELALLOC, we no longer set EXTENT_UPTODATE bit on
the extent_io_tree since uptodate status is being tracked by the bitmap
pointed to by page->private.

Signed-off-by: Chandan Rajendra <redacted>
---
 fs/btrfs/extent_io.c  | 150 ++++++++++++++++++++++++--------------------------
 fs/btrfs/file.c       |  17 ++++++
 fs/btrfs/inode.c      |  75 +++++++++++++++++++++----
 fs/btrfs/relocation.c |   3 +
 4 files changed, 155 insertions(+), 90 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a349f99..0adbff5 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c

@@ -1494,24 +1494,6 @@ void extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)
 	}
 }

-/*
- * helper function to set both pages and extents in the tree writeback
- */
-static void set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
-{
-	unsigned long index = start >> PAGE_SHIFT;
-	unsigned long end_index = end >> PAGE_SHIFT;
-	struct page *page;
-
-	while (index <= end_index) {
-		page = find_get_page(tree->mapping, index);
-		BUG_ON(!page); /* Pages should be in the extent_io_tree */
-		set_page_writeback(page);
-		put_page(page);
-		index++;
-	}
-}
-
 /* find the first state struct with 'bits' set after 'start', and
  * return it.  tree->lock must be held.  NULL will returned if
  * nothing was found after 'start'

@@ -2585,36 +2567,41 @@ void end_extent_writepage(struct page *page, int err, u64 start, u64 end)
  */
 static void end_bio_extent_writepage(struct bio *bio)
 {
+	struct btrfs_page_private *pg_private;
 	struct bio_vec *bvec;
+	unsigned long flags;
 	u64 start;
 	u64 end;
+	int clear_writeback;
 	int i;

 	bio_for_each_segment_all(bvec, bio, i) {
 		struct page *page = bvec->bv_page;
+		struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;

-		/* We always issue full-page reads, but if some block
-		 * in a page fails to read, blk_update_request() will
-		 * advance bv_offset and adjust bv_len to compensate.
-		 * Print a warning for nonzero offsets, and an error
-		 * if they don't add up to a full page.  */
-		if (bvec->bv_offset || bvec->bv_len != PAGE_SIZE) {
-			if (bvec->bv_offset + bvec->bv_len != PAGE_SIZE)
-				btrfs_err(BTRFS_I(page->mapping->host)->root->fs_info,
-				   "partial page write in btrfs with offset %u and length %u",
-					bvec->bv_offset, bvec->bv_len);
-			else
-				btrfs_info(BTRFS_I(page->mapping->host)->root->fs_info,
-				   "incomplete page write in btrfs with offset %u and "
-				   "length %u",
-					bvec->bv_offset, bvec->bv_len);
-		}
+		pg_private = NULL;
+		flags = 0;
+		clear_writeback = 1;

-		start = page_offset(page);
-		end = start + bvec->bv_offset + bvec->bv_len - 1;
+		start = page_offset(page) + bvec->bv_offset;
+		end = start + bvec->bv_len - 1;
+
+		if (root->sectorsize < PAGE_SIZE) {
+			pg_private = (struct btrfs_page_private *)page->private;
+			spin_lock_irqsave(&pg_private->io_lock, flags);
+		}

 		end_extent_writepage(page, bio->bi_error, start, end);
-		end_page_writeback(page);
+
+		if (root->sectorsize < PAGE_SIZE) {
+			clear_page_blks_state(page, 1 << BLK_STATE_IO, start,
+					end);
+			clear_writeback = page_io_complete(page);
+			spin_unlock_irqrestore(&pg_private->io_lock, flags);
+		}
+
+		if (clear_writeback)
+			end_page_writeback(page);
 	}

 	bio_put(bio);

@@ -3486,7 +3473,6 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 	u64 block_start;
 	u64 iosize;
 	sector_t sector;
-	struct extent_state *cached_state = NULL;
 	struct extent_map *em;
 	struct block_device *bdev;
 	size_t pg_offset = 0;

@@ -3538,20 +3524,29 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 							 page_end, NULL, 1);
 			break;
 		}
-		em = epd->get_extent(inode, page, pg_offset, cur,
-				     end - cur + 1, 1);
+
+		if (blocksize < PAGE_SIZE
+			&& !test_page_blks_state(page, BLK_STATE_DIRTY, cur,
+						cur + blocksize - 1, 1)) {
+			cur += blocksize;
+			continue;
+		}
+
+		pg_offset = cur & (PAGE_SIZE - 1);
+
+		em = epd->get_extent(inode, page, pg_offset, cur, blocksize, 1);
 		if (IS_ERR_OR_NULL(em)) {
 			SetPageError(page);
 			ret = PTR_ERR_OR_ZERO(em);
 			break;
 		}

-		extent_offset = cur - em->start;
 		em_end = extent_map_end(em);
 		BUG_ON(em_end <= cur);
 		BUG_ON(end < cur);
-		iosize = min(em_end - cur, end - cur + 1);
-		iosize = ALIGN(iosize, blocksize);
+
+		iosize = blocksize;
+		extent_offset = cur - em->start;
 		sector = (em->block_start + extent_offset) >> 9;
 		bdev = em->bdev;
 		block_start = em->block_start;

@@ -3559,65 +3554,64 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 		free_extent_map(em);
 		em = NULL;

-		/*
-		 * compressed and inline extents are written through other
-		 * paths in the FS
-		 */
-		if (compressed || block_start == EXTENT_MAP_HOLE ||
-		    block_start == EXTENT_MAP_INLINE) {
-			/*
-			 * end_io notification does not happen here for
-			 * compressed extents
-			 */
-			if (!compressed && tree->ops &&
-			    tree->ops->writepage_end_io_hook)
-				tree->ops->writepage_end_io_hook(page, cur,
-							 cur + iosize - 1,
-							 NULL, 1);
-			else if (compressed) {
-				/* we don't want to end_page_writeback on
-				 * a compressed extent.  this happens
-				 * elsewhere
-				 */
-				nr++;
-			}
+		ASSERT(!compressed);
+		ASSERT(block_start != EXTENT_MAP_INLINE);

+		if (block_start == EXTENT_MAP_HOLE) {
+			if (blocksize < PAGE_SIZE) {
+				if (test_page_blks_state(page, BLK_STATE_UPTODATE,
+								cur, cur + iosize - 1,
+								1)) {
+					clear_page_blks_state(page,
+							1 << BLK_STATE_DIRTY, cur,
+							cur + iosize - 1);
+				} else {
+					BUG();
+				}
+			} else if (!PageUptodate(page)) {
+					BUG();
+			}