[PATCH v4 16/18] f2fs: handle block cloning within the same large folio

[Nanzhe Zhao <nzzhao.sigma@gmail.com>]

From: Nanzhe Zhao <zhaonanzhe@xiaomi.com>

With large folios, the source and destination block in __clone_blkaddrs()
can belong to the same folio during same-inode operations such as
collapse range and insert range.

In that case, locking the source folio and then looking up the
destination folio can try to lock the same folio again.  It also copies
from and to offset 0, which is only correct for order-0 folios.

Detect the same-inode, same-folio case before looking up the destination
folio.  Then in this case,we reserve the destination block explicitly.

Signed-off-by: Nanzhe Zhao <zhaonanzhe@xiaomi.com>
---
 fs/f2fs/file.c | 61 +++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 53 insertions(+), 8 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 69d1344a5..3c90cd365 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1608,25 +1608,70 @@ static int __clone_blkaddrs(struct inode *src_inode, struct inode *dst_inode,
 			f2fs_put_dnode(&dn);
 		} else {
 			struct folio *fsrc, *fdst;
+			size_t src_off, dst_off;
+			bool same_folio;
 
 			fsrc = f2fs_get_lock_data_folio(src_inode,
 							src + i, true);
 			if (IS_ERR(fsrc))
 				return PTR_ERR(fsrc);
-			fdst = f2fs_get_new_data_folio(dst_inode, NULL, dst + i,
-								true);
-			if (IS_ERR(fdst)) {
-				f2fs_folio_put(fsrc, true);
-				return PTR_ERR(fdst);
+
+			src_off = offset_in_folio(fsrc,
+						(loff_t)(src + i) << PAGE_SHIFT);
+
+			/*
+			 * For same-inode operations (collapse/insert), src and
+			 * dst may fall within the same large folio. Detect this
+			 * to avoid self-deadlock on folio lock.
+			 */
+			same_folio = src_inode == dst_inode &&
+				     folio_contains(fsrc, dst + i);
+			if (same_folio) {
+				struct dnode_of_data dn;
+
+				/* Reserve block for dst before copying */
+				set_new_dnode(&dn, dst_inode, NULL, NULL, 0);
+				ret = f2fs_reserve_block(&dn, dst + i);
+				if (ret) {
+					f2fs_folio_put(fsrc, true);
+					return ret;
+				}
+				fdst = fsrc;
+			} else {
+				fdst = f2fs_get_new_data_folio(dst_inode, NULL,
+							      dst + i, true);
+				if (IS_ERR(fdst)) {
+					f2fs_folio_put(fsrc, true);
+					return PTR_ERR(fdst);
+				}
 			}
 
+			dst_off = offset_in_folio(fdst,
+					(loff_t)(dst + i) << PAGE_SHIFT);
 			f2fs_folio_wait_writeback(fdst, true, true);
-
-			memcpy_folio(fdst, 0, fsrc, 0, PAGE_SIZE);
+			memcpy_folio(fdst, dst_off, fsrc, src_off,
+				    PAGE_SIZE);
+			if (folio_test_large(fdst)) {
+				if (!f2fs_ffs_find_or_alloc(fdst)) {
+					f2fs_folio_put(fdst, true);
+					if (!same_folio)
+						f2fs_folio_put(fsrc, true);
+					return -ENOMEM;
+				}
+				f2fs_ffs_mark_subrange_uptodate(fdst,
+							dst_off, PAGE_SIZE);
+				f2fs_ffs_mark_subrange_dirty(fdst, dst_off,
+							    PAGE_SIZE);
+			}
 			folio_mark_dirty(fdst);
+			if (same_folio && i_size_read(dst_inode) <
+			    ((loff_t)(dst + i + 1) << PAGE_SHIFT))
+				f2fs_i_size_write(dst_inode,
+					((loff_t)(dst + i + 1) << PAGE_SHIFT));
 			folio_set_f2fs_gcing(fdst);
 			f2fs_folio_put(fdst, true);
-			f2fs_folio_put(fsrc, true);
+			if (!same_folio)
+				f2fs_folio_put(fsrc, true);
 
 			ret = f2fs_truncate_hole(src_inode,
 						src + i, src + i + 1);
-- 
2.43.0