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Commit be512691 authored by NeilBrown's avatar NeilBrown
Browse files

md: bitmap: improve bitmap maintenance code. 



The code for checking which bits in the bitmap can be cleared
has 2 problems:
 1/ it repeatedly takes and drops a spinlock, where it would make
    more sense to just hold on to it most of the time.
 2/ it doesn't make use of some opportunities to skip large sections
    of the bitmap

This patch fixes those.  It will only affect CPU consumption, not
correctness.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 2b69c839

drivers/md/bitmap.c

+7 −6
Original line number Diff line number Diff line
@@ -1097,14 +1097,12 @@ void bitmap_daemon_work(struct bitmap *bitmap) 
	}

	bitmap->allclean = 1;



	spin_lock_irqsave(&bitmap->lock, flags);

	for (j = 0; j < bitmap->chunks; j++) {

		bitmap_counter_t *bmc;

		spin_lock_irqsave(&bitmap->lock, flags);

		if (!bitmap->filemap) {

		if (!bitmap->filemap)

			/* error or shutdown */

			spin_unlock_irqrestore(&bitmap->lock, flags);

			break;

		}



		page = filemap_get_page(bitmap, j);
@@ -1121,6 +1119,8 @@ void bitmap_daemon_work(struct bitmap *bitmap) 
					write_page(bitmap, page, 0);

					bitmap->allclean = 0;

				}

				spin_lock_irqsave(&bitmap->lock, flags);

				j |= (PAGE_BITS - 1);

				continue;

			}
@@ -1181,9 +1181,10 @@ void bitmap_daemon_work(struct bitmap *bitmap) 
					ext2_clear_bit(file_page_offset(j), paddr);

				kunmap_atomic(paddr, KM_USER0);

			}

		} else

			j |= PAGE_COUNTER_MASK;

	}

	spin_unlock_irqrestore(&bitmap->lock, flags);

	}



	/* now sync the final page */

	if (lastpage != NULL) {