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Subject[PATCH 2/2] f2fs: fix a deadlock for summary page lock vs. sentry_lock
Date
In f2fs_gc:                      In f2fs_replace_block:
- lock_page(sum_page)
- check_valid_map() - mutex_lock(sentry_lock)
- mutex_lock(sentry_lock) - change_curseg()
- lock_page(sum_page)

This patch fixes the deadlock condition.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
fs/f2fs/gc.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 43354cb..e1e7361 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -750,6 +750,15 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,

sum = page_address(sum_page);

+ /*
+ * this is to avoid deadlock:
+ * - lock_page(sum_page) - f2fs_replace_block
+ * - check_valid_map() - mutex_lock(sentry_lock)
+ * - mutex_lock(sentry_lock) - change_curseg()
+ * - lock_page(sum_page)
+ */
+ unlock_page(sum_page);
+
switch (GET_SUM_TYPE((&sum->footer))) {
case SUM_TYPE_NODE:
gc_node_segment(sbi, sum->entries, segno, gc_type);
@@ -763,7 +772,7 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)), gc_type);
stat_inc_call_count(sbi->stat_info);

- f2fs_put_page(sum_page, 1);
+ f2fs_put_page(sum_page, 0);
}

int f2fs_gc(struct f2fs_sb_info *sbi)
--
2.1.1


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