It reports a bug from device w/ zufs:

F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
F2FS-fs (dm-64): Stopped filesystem due to reason: 4

Thread A                                Thread B
- f2fs_expand_inode_data
 - f2fs_allocate_pinning_section
  - f2fs_gc_range
   - do_garbage_collect w/ segno #x
                                        - writepage
                                         - f2fs_allocate_data_block
                                          - new_curseg
                                           - allocate segno #x

The root cause is: fallocate on pinning file may race w/ block allocation
as above, result in do_garbage_collect() from fallocate() may migrate
segment which is just allocated by a log, the log will update segment type
in its in-memory structure, however GC will get segment type from on-disk
SSA block, once segment type changes by log, we can detect such
inconsistency, then shutdown filesystem.

In this case, on-disk SSA shows type of segno #173822 is 1 (SUM_TYPE_NODE),
however segno #173822 was just allocated as data type segment, so in-memory
SIT shows type of segno #173822 is 0 (SUM_TYPE_DATA).

Change as below to fix this issue:
- check whether current section is empty before gc
- add sanity checks on do_garbage_collect() to avoid any race case, result
in migrating segment used by log.
- btw, it fixes misc issue in printed logs: "SSA and SIT" -> "SIT and SSA".

Fixes: 9703d69d9d15 ("f2fs: support file pinning for zoned devices")
Cc: Daeho Jeong <daehoje...@google.com>
Signed-off-by: Chao Yu <c...@kernel.org>
---
 fs/f2fs/gc.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index ed3acbfc83ca..a7708cf80c04 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1794,6 +1794,13 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
                struct folio *sum_folio = filemap_get_folio(META_MAPPING(sbi),
                                        GET_SUM_BLOCK(sbi, segno));
 
+               if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno))) {
+                       f2fs_err(sbi, "%s: segment %u is used by log",
+                                                       __func__, segno);
+                       f2fs_bug_on(sbi, 1);
+                       goto skip;
+               }
+
                if (get_valid_blocks(sbi, segno, false) == 0)
                        goto freed;
                if (gc_type == BG_GC && __is_large_section(sbi) &&
@@ -1805,7 +1812,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 
                sum = folio_address(sum_folio);
                if (type != GET_SUM_TYPE((&sum->footer))) {
-                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] 
in SSA and SIT",
+                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] 
in SIT and SSA",
                                 segno, type, GET_SUM_TYPE((&sum->footer)));
                        f2fs_stop_checkpoint(sbi, false,
                                STOP_CP_REASON_CORRUPTED_SUMMARY);
@@ -2068,6 +2075,13 @@ int f2fs_gc_range(struct f2fs_sb_info *sbi,
                        .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
                };
 
+               /*
+                * avoid migrating empty section, as it can be allocated by
+                * log in parallel.
+                */
+               if (!get_valid_blocks(sbi, segno, true))
+                       continue;
+
                if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno)))
                        continue;
 
-- 
2.49.0



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