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Commit 5f727395 authored by Jaegeuk Kim's avatar Jaegeuk Kim
Browse files

f2fs: fix deadlock during inline_data conversion 



A deadlock can be occurred:
Thread 1]                             Thread 2]
 - f2fs_write_data_pages              - f2fs_write_begin
   - lock_page(page #0)
                                        - grab_cache_page(page #X)
                                        - get_node_page(inode_page)
                                        - grab_cache_page(page #0)
                                          : to convert inline_data
   - f2fs_write_data_page
     - f2fs_write_inline_data
       - get_node_page(inode_page)

In this case, trying to lock inode_page and page #0 causes deadlock.
In order to avoid this, this patch adds a rule for this locking policy,
which is that page #0 should be locked followed by inode_page lock.

Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent ce3e6d25

fs/f2fs/data.c

+14 −14
Original line number Diff line number Diff line
@@ -936,6 +936,17 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping, 
	trace_f2fs_write_begin(inode, pos, len, flags);



	f2fs_balance_fs(sbi);



	/*

	 * We should check this at this moment to avoid deadlock on inode page

	 * and #0 page. The locking rule for inline_data conversion should be:

	 * lock_page(page #0) -> lock_page(inode_page)

	 */

	if (index != 0) {

		err = f2fs_convert_inline_inode(inode);

		if (err)

			goto fail;

	}

repeat:

	page = grab_cache_page_write_begin(mapping, index, flags);

	if (!page) {
@@ -960,22 +971,11 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping, 
			set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);

			sync_inode_page(&dn);

			goto put_next;

		} else if (page->index == 0) {

			err = f2fs_convert_inline_page(&dn, page);

			if (err)

				goto put_fail;

		} else {

			struct page *p = grab_cache_page(inode->i_mapping, 0);

			if (!p) {

				err = -ENOMEM;

				goto put_fail;

		}

			err = f2fs_convert_inline_page(&dn, p);

			f2fs_put_page(p, 1);

		err = f2fs_convert_inline_page(&dn, page);

		if (err)

			goto put_fail;

	}

	}

	err = f2fs_reserve_block(&dn, index);

	if (err)

		goto put_fail;