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: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 47c68bc..56df1ce 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1097,14 +1097,12 @@
}
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 @@
write_page(bitmap, page, 0);
bitmap->allclean = 0;
}
+ spin_lock_irqsave(&bitmap->lock, flags);
+ j |= (PAGE_BITS - 1);
continue;
}
@@ -1181,9 +1181,10 @@
ext2_clear_bit(file_page_offset(j), paddr);
kunmap_atomic(paddr, KM_USER0);
}
- }
- spin_unlock_irqrestore(&bitmap->lock, flags);
+ } else
+ j |= PAGE_COUNTER_MASK;
}
+ spin_unlock_irqrestore(&bitmap->lock, flags);
/* now sync the final page */
if (lastpage != NULL) {