[PATCH v2] f2fs: Fix indefinite loop in f2fs_gc()

[Sahitya Tummala]

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.

Signed-off-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
---
v2: fix as per Chao's suggestion to handle this error case

 fs/f2fs/gc.c      | 15 ++++++++++++++-
 fs/f2fs/segment.c |  5 +++++
 fs/f2fs/segment.h |  3 +++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 8974672..321a78a 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -382,6 +382,14 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 			nsearched++;
 		}
 
+		/*
+		 * skip selecting the invalid segno (that is failed due to block
+		 * validity check failed during GC) to avoid endless GC loop in
+		 * such cases.
+		 */
+		if (test_bit(segno, sm->invalid_segmap))
+			goto next;
+
 		secno = GET_SEC_FROM_SEG(sbi, segno);
 
 		if (sec_usage_check(sbi, secno))
@@ -975,6 +983,7 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 	int off;
 	int phase = 0;
 	int submitted = 0;
+	struct sit_info *sit_i = SIT_I(sbi);
 
 	start_addr = START_BLOCK(sbi, segno);
 
@@ -1008,8 +1017,12 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 		}
 
 		/* Get an inode by ino with checking validity */
-		if (!is_alive(sbi, entry, &dni, start_addr + off, &nofs))
+		if (!is_alive(sbi, entry, &dni, start_addr + off, &nofs)) {
+			if (!test_and_set_bit(segno, sit_i->invalid_segmap))
+				f2fs_err(sbi, "invalid blkaddr %u in seg %u is found\n",
+						start_addr + off, segno);
 			continue;
+		}
 
 		if (phase == 2) {
 			f2fs_ra_node_page(sbi, dni.ino);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index a661ac3..d45a1d3 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -4017,6 +4017,10 @@ static int build_sit_info(struct f2fs_sb_info *sbi)
 		return -ENOMEM;
 #endif
 
+	sit_i->invalid_segmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
+	if (!sit_i->invalid_segmap)
+		return -ENOMEM;
+
 	/* init SIT information */
 	sit_i->s_ops = &default_salloc_ops;
 
@@ -4518,6 +4522,7 @@ static void destroy_sit_info(struct f2fs_sb_info *sbi)
 #ifdef CONFIG_F2FS_CHECK_FS
 	kvfree(sit_i->sit_bitmap_mir);
 #endif
+	kvfree(sit_i->invalid_segmap);
 	kvfree(sit_i);
 }
 
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index b746028..bc5dbe8 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -246,6 +246,9 @@ struct sit_info {
 	unsigned long long min_mtime;		/* min. modification time */
 	unsigned long long max_mtime;		/* max. modification time */
 
+	/* list of segments to be ignored by GC in case of errors */
+	unsigned long *invalid_segmap;
+
 	unsigned int last_victim[MAX_GC_POLICY]; /* last victim segment # */
 };
 
-- 
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