fs-writeback: Add helper function to start writeback if idle (17bd55d0) · Commits · 戴 / test

ext4, at least, would like to start pushing on writeback if it starts to get close to ENOSPC when reserving worst-case blocks for delalloc writes. Writing out delalloc data will convert those worst-case predictions into usually smaller actual usage, freeing up space before we hit ENOSPC based on this speculation. Thanks to Jens for the suggestion for the helper function, & the naming help. I've made the helper return status on whether writeback was started even though I don't plan to use it in the ext4 patch; it seems like it would be potentially useful to test this in some cases. Signed-off-by:

Eric Sandeen <sandeen@redhat.com> Acked-by:

Jan Kara <jack@suse.cz>

fs/fs-writeback.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -1186,6 +1186,23 @@ void writeback_inodes_sb(struct super_block *sb)
		}
		EXPORT_SYMBOL(writeback_inodes_sb);

		/**
		* writeback_inodes_sb_if_idle - start writeback if none underway
		* @sb: the superblock
		*
		* Invoke writeback_inodes_sb if no writeback is currently underway.
		* Returns 1 if writeback was started, 0 if not.
		*/
		int writeback_inodes_sb_if_idle(struct super_block *sb)
		{
		if (!writeback_in_progress(sb->s_bdi)) {
		writeback_inodes_sb(sb);
		return 1;
		} else
		return 0;
		}
		EXPORT_SYMBOL(writeback_inodes_sb_if_idle);

		/**
		* sync_inodes_sb - sync sb inode pages
		* @sb: the superblock

include/linux/writeback.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -70,6 +70,7 @@ struct writeback_control {
		struct bdi_writeback;
		int inode_wait(void *);
		void writeback_inodes_sb(struct super_block *);
		int writeback_inodes_sb_if_idle(struct super_block *);
		void sync_inodes_sb(struct super_block *);
		void writeback_inodes_wbc(struct writeback_control *wbc);
		long wb_do_writeback(struct bdi_writeback *wb, int force_wait);

Admin message