[PATCH 09/14] f2fs: support partial uptodate large folio read

[Nanzhe Zhao]

Buffered write can have write bytes smaller than folio
size for cases when folio minimum order is not zero.
This can left partially uptodate folio in page cache.
So we skip uptodate subpage read in read_data_large_folio.
Also mark hole subpage uptodate in uptodate bitmap.

Signed-off-by: Nanzhe Zhao <zhaonanzhe@xxxxxxxxxx>
---
 fs/f2fs/data.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 48c1bb6c02e3..59b07b83b216 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2855,6 +2855,56 @@ static bool find_next_valid_block(const struct folio *folio,
 	return false;
 }
 
+static unsigned int ffs_next_uptodate_subpage(struct f2fs_folio_state *ffs,
+			unsigned int start, unsigned int end)
+{
+	return find_next_bit(ffs->state, end + 1, start);
+}
+
+static unsigned int ffs_next_nonuptodate_subpage(struct f2fs_folio_state *ffs,
+			unsigned int start, unsigned int end)
+{
+	return find_next_zero_bit(ffs->state, end + 1, start);
+}
+
+static void f2fs_skip_fully_uptodate_front(struct folio *folio,
+			pgoff_t *index, pgoff_t *offset, unsigned int *nrpages,
+			unsigned int *max_nr_pages)
+{
+	struct f2fs_folio_state *ffs;
+	unsigned int next, skipped;
+
+	if (!f2fs_folio_has_ffs(folio) || !*nrpages)
+		return;
+
+	ffs = folio->private;
+	next = ffs_next_nonuptodate_subpage(ffs, *offset,
+					    *offset + *nrpages - 1);
+	skipped = next - *offset;
+	if (!skipped)
+		return;
+
+	*index += skipped;
+	*offset += skipped;
+	*nrpages -= skipped;
+	*max_nr_pages -= skipped;
+}
+
+static void f2fs_truncate_read_extent(struct folio *folio, pgoff_t offset,
+				     unsigned int *len_blks)
+{
+	struct f2fs_folio_state *ffs;
+	unsigned int next, end;
+
+	if (!f2fs_folio_has_ffs(folio) || *len_blks <= 1)
+		return;
+
+	ffs = folio->private;
+	end = offset + *len_blks - 1;
+	next = ffs_next_uptodate_subpage(ffs, offset + 1, end);
+	if (next <= end)
+		*len_blks = next - offset;
+}
 static int f2fs_read_data_large_folio(struct inode *inode,
 		struct fsverity_info *vi,
 		struct readahead_control *rac, struct folio *folio)
@@ -2901,6 +2951,11 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 
 		len_blks = 1;
 
+		f2fs_skip_fully_uptodate_front(folio, &index, &offset,
+					       &nrpages, &max_nr_pages);
+		if (!nrpages)
+			break;
+
 		/*
 		 * Map blocks using the previous result first.
 		 */
@@ -2933,6 +2988,7 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 			len_blks = min_t(unsigned int, nrpages, max_nr_pages);
 			len_blks = min_t(unsigned int, len_blks,
 					(unsigned int)(map.m_lblk + map.m_len - index));
+			f2fs_truncate_read_extent(folio, offset, &len_blks);
 
 			for (i = 0; i < len_blks; i++) {
 				if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode),
@@ -2959,6 +3015,13 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 				ret = -EIO;
 				goto err_out;
 			}
+			if (folio_test_large(folio)) {
+				ffs = f2fs_ffs_find_or_alloc(folio);
+				spin_lock_irq(&ffs->state_lock);
+				__ffs_mark_subrange_uptodate(folio, ffs,
+						page_offset, PAGE_SIZE);
+				spin_unlock_irq(&ffs->state_lock);
+			}
 			continue;
 		}
 
-- 
2.43.0