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md: bitmap: improve bitmap maintenance code.

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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>
This commit is contained in:
NeilBrown 2009-05-26 09:41:17 +10:00
parent 2b69c83924
commit be51269103
1 changed files with 7 additions and 6 deletions
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13
drivers/md/bitmap.c
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@ -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);
}
}
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) {