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Subject[PATCH v4] f2fs: Fix indefinite loop in f2fs_gc()
Date
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>
---
v4: Cover all logic with CONFIG_F2FS_CHECK_FS

fs/f2fs/gc.c | 31 +++++++++++++++++++++++++++++--
fs/f2fs/segment.c | 14 +++++++++++++-
fs/f2fs/segment.h | 3 +++
3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 8974672..cbcacbd 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))
@@ -602,8 +612,15 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
{
struct page *node_page;
nid_t nid;
- unsigned int ofs_in_node;
+ unsigned int ofs_in_node, segno;
block_t source_blkaddr;
+ unsigned long offset;
+#ifdef CONFIG_F2FS_CHECK_FS
+ struct sit_info *sit_i = SIT_I(sbi);
+#endif
+
+ segno = GET_SEGNO(sbi, blkaddr);
+ offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);

nid = le32_to_cpu(sum->nid);
ofs_in_node = le16_to_cpu(sum->ofs_in_node);
@@ -627,8 +644,18 @@ 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
+ if (unlikely(check_valid_map(sbi, segno, offset))) {
+ if (!test_and_set_bit(segno, sit_i->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;
}

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index a661ac3..ee795b1 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -806,6 +806,9 @@ static void __remove_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
enum dirty_type dirty_type)
{
struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
+#ifdef CONFIG_F2FS_CHECK_FS
+ struct sit_info *sit_i = SIT_I(sbi);
+#endif

if (test_and_clear_bit(segno, dirty_i->dirty_segmap[dirty_type]))
dirty_i->nr_dirty[dirty_type]--;
@@ -817,9 +820,13 @@ static void __remove_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
if (test_and_clear_bit(segno, dirty_i->dirty_segmap[t]))
dirty_i->nr_dirty[t]--;

- if (get_valid_blocks(sbi, segno, true) == 0)
+ if (get_valid_blocks(sbi, segno, true) == 0) {
clear_bit(GET_SEC_FROM_SEG(sbi, segno),
dirty_i->victim_secmap);
+#ifdef CONFIG_F2FS_CHECK_FS
+ clear_bit(segno, sit_i->invalid_segmap);
+#endif
+ }
}
}

@@ -4015,6 +4022,10 @@ static int build_sit_info(struct f2fs_sb_info *sbi)
sit_i->sit_bitmap_mir = kmemdup(src_bitmap, bitmap_size, GFP_KERNEL);
if (!sit_i->sit_bitmap_mir)
return -ENOMEM;
+
+ sit_i->invalid_segmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
+ if (!sit_i->invalid_segmap)
+ return -ENOMEM;
#endif

/* init SIT information */
@@ -4517,6 +4528,7 @@ static void destroy_sit_info(struct f2fs_sb_info *sbi)
kvfree(sit_i->sit_bitmap);
#ifdef CONFIG_F2FS_CHECK_FS
kvfree(sit_i->sit_bitmap_mir);
+ kvfree(sit_i->invalid_segmap);
#endif
kvfree(sit_i);
}
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index b746028..9370d53 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -229,6 +229,9 @@ struct sit_info {
char *sit_bitmap; /* SIT bitmap pointer */
#ifdef CONFIG_F2FS_CHECK_FS
char *sit_bitmap_mir; /* SIT bitmap mirror */
+
+ /* bitmap of segments to be ignored by GC in case of errors */
+ unsigned long *invalid_segmap;
#endif
unsigned int bitmap_size; /* SIT bitmap size */

--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
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