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Commit 2d41291c authored by Sahitya Tummala's avatar Sahitya Tummala Committed by Jaegeuk Kim
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f2fs: fix the panic in do_checkpoint() 



There could be a scenario where f2fs_sync_meta_pages() will not
ensure that all F2FS_DIRTY_META pages are submitted for IO. Thus,
resulting in the below panic in do_checkpoint() -

f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) &&
				!f2fs_cp_error(sbi));

This can happen in a low-memory condition, where shrinker could
also be doing the writepage operation (stack shown below)
at the same time when checkpoint is running on another core.

schedule
down_write
f2fs_submit_page_write -> by this time, this page in page cache is tagged
			as PAGECACHE_TAG_WRITEBACK and PAGECACHE_TAG_DIRTY
			is cleared, due to which f2fs_sync_meta_pages()
			cannot sync this page in do_checkpoint() path.
f2fs_do_write_meta_page
__f2fs_write_meta_page
f2fs_write_meta_page
shrink_page_list
shrink_inactive_list
shrink_node_memcg
shrink_node
kswapd

Signed-off-by: default avatarSahitya Tummala <stummala@codeaurora.org>
Reviewed-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent fc414c6c

fs/f2fs/checkpoint.c

+7 −9
Original line number Diff line number Diff line
@@ -1250,20 +1250,20 @@ static void unblock_operations(struct f2fs_sb_info *sbi) 
	f2fs_unlock_all(sbi);

}



void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi)

void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)

{

	DEFINE_WAIT(wait);



	for (;;) {

		prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);



		if (!get_pages(sbi, F2FS_WB_CP_DATA))

		if (!get_pages(sbi, type))

			break;



		if (unlikely(f2fs_cp_error(sbi)))

			break;



		io_schedule_timeout(5*HZ);

		io_schedule_timeout(HZ/50);

	}

	finish_wait(&sbi->cp_wait, &wait);

}
@@ -1384,8 +1384,6 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) 


	/* Flush all the NAT/SIT pages */

	f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO);

	f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) &&

					!f2fs_cp_error(sbi));



	/*

	 * modify checkpoint
@@ -1493,11 +1491,11 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) 


	/* Here, we have one bio having CP pack except cp pack 2 page */

	f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO);

	f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) &&

					!f2fs_cp_error(sbi));

	/* Wait for all dirty meta pages to be submitted for IO */

	f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META);



	/* wait for previous submitted meta pages writeback */

	f2fs_wait_on_all_pages_writeback(sbi);

	f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA);



	/* flush all device cache */

	err = f2fs_flush_device_cache(sbi);
@@ -1506,7 +1504,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) 


	/* barrier and flush checkpoint cp pack 2 page if it can */

	commit_checkpoint(sbi, ckpt, start_blk);

	f2fs_wait_on_all_pages_writeback(sbi);

	f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA);



	/*

	 * invalidate intermediate page cache borrowed from meta inode which are

fs/f2fs/f2fs.h

+1 −1
Original line number Diff line number Diff line
@@ -3307,7 +3307,7 @@ int f2fs_get_valid_checkpoint(struct f2fs_sb_info *sbi); 
void f2fs_update_dirty_page(struct inode *inode, struct page *page);

void f2fs_remove_dirty_inode(struct inode *inode);

int f2fs_sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type);

void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi);

void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type);

int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc);

void f2fs_init_ino_entry_info(struct f2fs_sb_info *sbi);

int __init f2fs_create_checkpoint_caches(void);

fs/f2fs/super.c

+1 −1
Original line number Diff line number Diff line
@@ -1180,7 +1180,7 @@ static void f2fs_put_super(struct super_block *sb) 
	/* our cp_error case, we can wait for any writeback page */

	f2fs_flush_merged_writes(sbi);



	f2fs_wait_on_all_pages_writeback(sbi);

	f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA);



	f2fs_bug_on(sbi, sbi->fsync_node_num);