Commit 3afae09f authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: compress: fix potential deadlock 



generic/269 reports a hangtask issue, the root cause is ABBA deadlock
described as below:

Thread A			Thread B
- down_write(&sbi->gc_lock) -- A
				- f2fs_write_data_pages
				 - lock all pages in cluster -- B
				 - f2fs_write_multi_pages
				  - f2fs_write_raw_pages
				   - f2fs_write_single_data_page
				    - f2fs_balance_fs
				     - down_write(&sbi->gc_lock) -- A
- f2fs_gc
 - do_garbage_collect
  - ra_data_block
   - pagecache_get_page -- B

To fix this, it needs to avoid calling f2fs_balance_fs() if there is
still cluster pages been locked in context of cluster writeback, so
instead, let's call f2fs_balance_fs() in the end of
f2fs_write_raw_pages() when all cluster pages were unlocked.

Fixes: 4c8ff709 ("f2fs: support data compression")
Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent 794c43f7

fs/f2fs/compress.c

+4 −1
Original line number Diff line number Diff line
@@ -1455,7 +1455,7 @@ static int f2fs_write_raw_pages(struct compress_ctx *cc, 


		ret = f2fs_write_single_data_page(cc->rpages[i], &_submitted,

						NULL, NULL, wbc, io_type,

						compr_blocks);

						compr_blocks, false);

		if (ret) {

			if (ret == AOP_WRITEPAGE_ACTIVATE) {

				unlock_page(cc->rpages[i]);
@@ -1490,6 +1490,9 @@ static int f2fs_write_raw_pages(struct compress_ctx *cc, 


		*submitted += _submitted;

	}



	f2fs_balance_fs(F2FS_M_SB(mapping), true);



	return 0;

out_err:

	for (++i; i < cc->cluster_size; i++) {

fs/f2fs/data.c

+6 −4
Original line number Diff line number Diff line
@@ -2671,7 +2671,8 @@ int f2fs_write_single_data_page(struct page *page, int *submitted, 
				sector_t *last_block,

				struct writeback_control *wbc,

				enum iostat_type io_type,

				int compr_blocks)

				int compr_blocks,

				bool allow_balance)

{

	struct inode *inode = page->mapping->host;

	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
@@ -2809,7 +2810,7 @@ int f2fs_write_single_data_page(struct page *page, int *submitted, 
	}

	unlock_page(page);

	if (!S_ISDIR(inode->i_mode) && !IS_NOQUOTA(inode) &&

					!F2FS_I(inode)->cp_task)

			!F2FS_I(inode)->cp_task && allow_balance)

		f2fs_balance_fs(sbi, need_balance_fs);



	if (unlikely(f2fs_cp_error(sbi))) {
@@ -2856,7 +2857,7 @@ static int f2fs_write_data_page(struct page *page, 
#endif



	return f2fs_write_single_data_page(page, NULL, NULL, NULL,

						wbc, FS_DATA_IO, 0);

						wbc, FS_DATA_IO, 0, true);

}



/*
@@ -3024,7 +3025,8 @@ static int f2fs_write_cache_pages(struct address_space *mapping, 
			}

#endif

			ret = f2fs_write_single_data_page(page, &submitted,

					&bio, &last_block, wbc, io_type, 0);

					&bio, &last_block, wbc, io_type,

					0, true);

			if (ret == AOP_WRITEPAGE_ACTIVATE)

				unlock_page(page);

#ifdef CONFIG_F2FS_FS_COMPRESSION

fs/f2fs/f2fs.h

+1 −1
Original line number Diff line number Diff line
@@ -3502,7 +3502,7 @@ int f2fs_write_single_data_page(struct page *page, int *submitted, 
				struct bio **bio, sector_t *last_block,

				struct writeback_control *wbc,

				enum iostat_type io_type,

				int compr_blocks);

				int compr_blocks, bool allow_balance);

void f2fs_invalidate_page(struct page *page, unsigned int offset,

			unsigned int length);

int f2fs_release_page(struct page *page, gfp_t wait);