f2fs: Fix indefinite loop in f2fs_gc()

Policy - Foreground GC, LFS and greedy GC mode.

Under this policy, f2fs_gc() loops forever to GC as it doesn't have
enough free segements to proceed and thus it keeps calling gc_more
for the same victim segment.  This can happen if the selected victim
segment could not be GC'd due to failed blkaddr validity check i.e.
is_alive() returns false for the blocks set in current validity map.

Fix this by keeping track of such invalid segments and skip those
segments for selection in get_victim_by_default() to avoid endless
GC loop under such error scenarios. Currently, add this logic under
CONFIG_F2FS_CHECK_FS to be able to root cause the issue in debug
version.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
[Jaegeuk Kim: fix wrong bitmap size]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 24 insertions, 1 deletions

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 8974672db78f..e88f98ddf396 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -382,6 +382,16 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 			nsearched++;
 		}
 
+#ifdef CONFIG_F2FS_CHECK_FS
+		/*
+		 * skip selecting the invalid segno (that is failed due to block
+		 * validity check failure during GC) to avoid endless GC loop in
+		 * such cases.
+		 */
+		if (test_bit(segno, sm->invalid_segmap))
+			goto next;
+#endif
+
 		secno = GET_SEC_FROM_SEG(sbi, segno);
 
 		if (sec_usage_check(sbi, secno))
@@ -627,8 +637,21 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 	source_blkaddr = datablock_addr(NULL, node_page, ofs_in_node);
 	f2fs_put_page(node_page, 1);
 
-	if (source_blkaddr != blkaddr)
+	if (source_blkaddr != blkaddr) {
+#ifdef CONFIG_F2FS_CHECK_FS
+		unsigned int segno = GET_SEGNO(sbi, blkaddr);
+		unsigned long offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);
+
+		if (unlikely(check_valid_map(sbi, segno, offset))) {
+			if (!test_and_set_bit(segno, SIT_I(sbi)->invalid_segmap)) {
+				f2fs_err(sbi, "mismatched blkaddr %u (source_blkaddr %u) in seg %u\n",
+						blkaddr, source_blkaddr, segno);
+				f2fs_bug_on(sbi, 1);
+			}
+		}
+#endif
 		return false;
+	}
 	return true;
 }