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Commit 420829d8 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
Browse files

btrfs: Refactor shrink_delalloc 



Add a couple of comments regarding the logic flow in shrink_delalloc.
Then, cease using max_reclaim as a temporary variable when calculating
nr_pages. Finally give max_reclaim a more becoming name, which
uneqivocally shows at what this variable really holds. No functional
changes.

Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 4546d178

fs/btrfs/extent-tree.c

+22 −11
Original line number Diff line number Diff line
@@ -4741,7 +4741,7 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim, 
	struct btrfs_space_info *space_info;

	struct btrfs_trans_handle *trans;

	u64 delalloc_bytes;

	u64 max_reclaim;

	u64 async_pages;

	u64 items;

	long time_left;

	unsigned long nr_pages;
@@ -4766,25 +4766,36 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim, 


	loops = 0;

	while (delalloc_bytes && loops < 3) {

		max_reclaim = min(delalloc_bytes, to_reclaim);

		nr_pages = max_reclaim >> PAGE_SHIFT;

		nr_pages = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;



		/*

		 * Triggers inode writeback for up to nr_pages. This will invoke

		 * ->writepages callback and trigger delalloc filling

		 *  (btrfs_run_delalloc_range()).

		 */

		btrfs_writeback_inodes_sb_nr(fs_info, nr_pages, items);



		/*

		 * We need to wait for the async pages to actually start before

		 * we do anything.

		 * We need to wait for the compressed pages to start before

		 * we continue.

		 */

		max_reclaim = atomic_read(&fs_info->async_delalloc_pages);

		if (!max_reclaim)

		async_pages = atomic_read(&fs_info->async_delalloc_pages);

		if (!async_pages)

			goto skip_async;



		if (max_reclaim <= nr_pages)

			max_reclaim = 0;

		/*

		 * Calculate how many compressed pages we want to be written

		 * before we continue. I.e if there are more async pages than we

		 * require wait_event will wait until nr_pages are written.

		 */

		if (async_pages <= nr_pages)

			async_pages = 0;

		else

			max_reclaim -= nr_pages;

			async_pages -= nr_pages;



		wait_event(fs_info->async_submit_wait,

			   atomic_read(&fs_info->async_delalloc_pages) <=

			   (int)max_reclaim);

			   (int)async_pages);

skip_async:

		spin_lock(&space_info->lock);

		if (list_empty(&space_info->tickets) &&