ext4: prevent partial update of the extent blocks (8583d2ea) · Commits · e / devices / android_kernel_fairphone_FP5

commit 0f2f87d51aebcf71a709b52f661d681594c7dffa upstream. In the most error path of current extents updating operations are not roll back partial updates properly when some bad things happens(.e.g in ext4_ext_insert_extent()). So we may get an inconsistent extents tree if journal has been aborted due to IO error, which may probability lead to BUGON later when we accessing these extent entries in errors=continue mode. This patch drop extent buffer's verify flag before updatng the contents in ext4_ext_get_access(), and reset it after updating in __ext4_ext_dirty(). After this patch we could force to check the extent buffer if extents tree updating was break off, make sure the extents are consistent. Signed-off-by:

Zhang Yi <yi.zhang@huawei.com> Reviewed-by:

Theodore Ts'o <tytso@mit.edu> Link: https://lore.kernel.org/r/20210908120850.4012324-4-yi.zhang@huawei.com Signed-off-by:

Theodore Ts'o <tytso@mit.edu> Signed-off-by:

Leah Rumancik <leah.rumancik@gmail.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ext4/extents.c

+16 −2

Original line number	Diff line number	Diff line
		@@ -133,14 +133,25 @@ static int ext4_ext_truncate_extend_restart(handle_t *handle,
		static int ext4_ext_get_access(handle_t handle, struct inode inode,
		struct ext4_ext_path *path)
		{
		int err = 0;

		if (path->p_bh) {
		/* path points to block */
		BUFFER_TRACE(path->p_bh, "get_write_access");
		return ext4_journal_get_write_access(handle, path->p_bh);
		err = ext4_journal_get_write_access(handle, path->p_bh);

		/*
		* The extent buffer's verified bit will be set again in
		* __ext4_ext_dirty(). We could leave an inconsistent
		* buffer if the extents updating procudure break off du
		* to some error happens, force to check it again.
		*/
		if (!err)
		clear_buffer_verified(path->p_bh);
		}
		/* path points to leaf/index in inode body */
		/* we use in-core data, no need to protect them */
		return 0;
		return err;
		}

		/*
		@@ -160,6 +171,9 @@ int __ext4_ext_dirty(const char where, unsigned int line, handle_t handle,
		/* path points to block */
		err = __ext4_handle_dirty_metadata(where, line, handle,
		inode, path->p_bh);
		/* Extents updating done, re-set verified flag */
		if (!err)
		set_buffer_verified(path->p_bh);
		} else {
		/* path points to leaf/index in inode body */
		err = ext4_mark_inode_dirty(handle, inode);