f2fs: add 'folio_in_bio' to handle readahead folios with no BIO submission

f2fs_read_data_large_folio() can build a single read BIO across multiple
folios during readahead. If a folio ends up having none of its subpages
added to the BIO (e.g. all subpages are zeroed / treated as holes), it
will never be seen by f2fs_finish_read_bio(), so folio_end_read() is
never called. This leaves the folio locked and not marked uptodate.

Track whether the current folio has been added to a BIO via a local
'folio_in_bio' bool flag, and when iterating readahead folios, explicitly
mark the folio uptodate (on success) and unlock it when nothing was added.

Signed-off-by: Nanzhe Zhao <nzzhao@126.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: sigmanature

fs/f2fs/data.c

@@ -2448,6 +2448,7 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 	unsigned nrpages;
 	struct f2fs_folio_state *ffs;
 	int ret = 0;
+	bool folio_in_bio;
 
 	if (!IS_IMMUTABLE(inode))
 		return -EOPNOTSUPP;
@@ -2463,6 +2464,7 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 	if (!folio)
 		goto out;
 
+	folio_in_bio = false;
 	index = folio->index;
 	offset = 0;
 	ffs = NULL;
@@ -2548,6 +2550,7 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 					offset << PAGE_SHIFT))
 			goto submit_and_realloc;
 
+		folio_in_bio = true;
 		inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
 		f2fs_update_iostat(F2FS_I_SB(inode), NULL, FS_DATA_READ_IO,
 				F2FS_BLKSIZE);
@@ -2557,6 +2560,10 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 	}
 	trace_f2fs_read_folio(folio, DATA);
 	if (rac) {
+		if (!folio_in_bio) {
+			folio_mark_uptodate(folio);
+			folio_unlock(folio);
+		}
 		folio = readahead_folio(rac);
 		goto next_folio;
 	}