Commit 638164a2 authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: fix potential panic during fstrim 



As Ju Hyung Park reported:

"When 'fstrim' is called for manual trim, a BUG() can be triggered
randomly with this patch.

I'm seeing this issue on both x86 Desktop and arm64 Android phone.

On x86 Desktop, this was caused during Ubuntu boot-up. I have a
cronjob installed which calls 'fstrim -v /' during boot. On arm64
Android, this was caused during GC looping with 1ms gc_min_sleep_time
& gc_max_sleep_time."

Root cause of this issue is that f2fs_wait_discard_bios can only be
used by f2fs_put_super, because during put_super there must be no
other referrers, so it can ignore discard entry's reference count
when removing the entry, otherwise in other caller we will hit bug_on
in __remove_discard_cmd as there may be other issuer added reference
count in discard entry.

Thread A				Thread B
					- issue_discard_thread
- f2fs_ioc_fitrim
 - f2fs_trim_fs
  - f2fs_wait_discard_bios
   - __issue_discard_cmd
    - __submit_discard_cmd
					 - __wait_discard_cmd
					  - dc->ref++
					  - __wait_one_discard_bio
   - __wait_discard_cmd
    - __remove_discard_cmd
     - f2fs_bug_on(sbi, dc->ref)

Fixes: 969d1b18
Reported-by: default avatarJu Hyung Park <qkrwngud825@gmail.com>
Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent e365806a

fs/f2fs/f2fs.h

+1 −1
Original line number Diff line number Diff line
@@ -2525,7 +2525,7 @@ void invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr); 
bool is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);

void refresh_sit_entry(struct f2fs_sb_info *sbi, block_t old, block_t new);

void stop_discard_thread(struct f2fs_sb_info *sbi);

void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi);

void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount);

void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc);

void release_discard_addrs(struct f2fs_sb_info *sbi);

int npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);

fs/f2fs/segment.c

+3 −3
Original line number Diff line number Diff line
@@ -1210,11 +1210,11 @@ void stop_discard_thread(struct f2fs_sb_info *sbi) 
}



/* This comes from f2fs_put_super and f2fs_trim_fs */

void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)

void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount)

{

	__issue_discard_cmd(sbi, false);

	__drop_discard_cmd(sbi);

	__wait_discard_cmd(sbi, false);

	__wait_discard_cmd(sbi, !umount);

}



static void mark_discard_range_all(struct f2fs_sb_info *sbi)
@@ -2244,7 +2244,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range) 
	}

	/* It's time to issue all the filed discards */

	mark_discard_range_all(sbi);

	f2fs_wait_discard_bios(sbi);

	f2fs_wait_discard_bios(sbi, false);

out:

	range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);

	return err;

fs/f2fs/super.c

+1 −1
Original line number Diff line number Diff line
@@ -801,7 +801,7 @@ static void f2fs_put_super(struct super_block *sb) 
	}



	/* be sure to wait for any on-going discard commands */

	f2fs_wait_discard_bios(sbi);

	f2fs_wait_discard_bios(sbi, true);



	if (f2fs_discard_en(sbi) && !sbi->discard_blks) {

		struct cp_control cpc = {

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