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Commit 8a5e9cf1 authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
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[PATCH] md: make sure md/bitmap doesn't try to write a page with active writeback 



Due to the use of write-behind, it is possible for md to write a page to
the bitmap file that is still completing writeback.  This is not allowed.

With this patch, we detect those cases and either force a sync write, or
back off and try later, as appropriate.

Signed-off-by: default avatarNeil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 39730960

drivers/md/bitmap.c

+38 −30
Original line number Diff line number Diff line
@@ -313,7 +313,16 @@ static int write_page(struct bitmap *bitmap, struct page *page, int wait) 
	if (bitmap->file == NULL)

		return write_sb_page(bitmap->mddev, bitmap->offset, page, wait);



	if (wait)

		lock_page(page);

	else {

		if (TestSetPageLocked(page))

			return -EAGAIN; /* already locked */

		if (PageWriteback(page)) {

			unlock_page(page);

			return -EAGAIN;

		}

	}



	ret = page->mapping->a_ops->prepare_write(NULL, page, 0, PAGE_SIZE);

	if (!ret)
@@ -400,7 +409,7 @@ int bitmap_update_sb(struct bitmap *bitmap) 
	if (!bitmap->mddev->degraded)

		sb->events_cleared = cpu_to_le64(bitmap->mddev->events);

	kunmap(bitmap->sb_page);

	return write_page(bitmap, bitmap->sb_page, 0);

	return write_page(bitmap, bitmap->sb_page, 1);

}



/* print out the bitmap file superblock */
@@ -762,6 +771,7 @@ int bitmap_unplug(struct bitmap *bitmap) 
	unsigned long i, attr, flags;

	struct page *page;

	int wait = 0;

	int err;



	if (!bitmap)

		return 0;
@@ -782,10 +792,18 @@ int bitmap_unplug(struct bitmap *bitmap) 
			wait = 1;

		spin_unlock_irqrestore(&bitmap->lock, flags);



		if (attr & (BITMAP_PAGE_DIRTY | BITMAP_PAGE_NEEDWRITE))

			if (write_page(bitmap, page, 0))

		if (attr & (BITMAP_PAGE_DIRTY | BITMAP_PAGE_NEEDWRITE)) {

			err = write_page(bitmap, page, 0);

			if (err == -EAGAIN) {

				if (attr & BITMAP_PAGE_DIRTY)

					err = write_page(bitmap, page, 1);

				else

					err = 0;

			}

			if (err)

				return 1;

		}

	}

	if (wait) { /* if any writes were performed, we need to wait on them */

		if (bitmap->file) {

			spin_lock_irq(&bitmap->write_lock);
@@ -1006,8 +1024,15 @@ int bitmap_daemon_work(struct bitmap *bitmap) 
				}

				spin_unlock_irqrestore(&bitmap->lock, flags);

				if (attr & BITMAP_PAGE_NEEDWRITE) {

					if (write_page(bitmap, page, 0))

					switch (write_page(bitmap, page, 0)) {

					case -EAGAIN:

						set_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);

						break;

					case 0:

						break;

					default:

						bitmap_file_kick(bitmap);

					}

					page_cache_release(page);

				}

				continue;
@@ -1020,6 +1045,10 @@ int bitmap_daemon_work(struct bitmap *bitmap) 
					clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);

					spin_unlock_irqrestore(&bitmap->lock, flags);

					err = write_page(bitmap, lastpage, 0);

					if (err == -EAGAIN) {

						err = 0;

						set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);

					}

				} else {

					set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);

					spin_unlock_irqrestore(&bitmap->lock, flags);
@@ -1068,6 +1097,10 @@ int bitmap_daemon_work(struct bitmap *bitmap) 
			clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);

			spin_unlock_irqrestore(&bitmap->lock, flags);

			err = write_page(bitmap, lastpage, 0);

			if (err == -EAGAIN) {

				set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);

				err = 0;

			}

		} else {

			set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);

			spin_unlock_irqrestore(&bitmap->lock, flags);
@@ -1421,31 +1454,6 @@ static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, 
	}

}



/* dirty the entire bitmap */

int bitmap_setallbits(struct bitmap *bitmap)

{

	unsigned long flags;

	unsigned long j;



	/* dirty the in-memory bitmap */

	bitmap_set_memory_bits(bitmap, 0, bitmap->chunks << CHUNK_BLOCK_SHIFT(bitmap), 1);



	/* dirty the bitmap file */

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

		struct page *page = bitmap->filemap[j];



		spin_lock_irqsave(&bitmap->lock, flags);

		page_cache_get(page);

		spin_unlock_irqrestore(&bitmap->lock, flags);

		memset(kmap(page), 0xff, PAGE_SIZE);

		kunmap(page);

		if (write_page(bitmap, page, 0))

			return 1;

	}



	return 0;

}



/*

 * free memory that was allocated

 */