Commit 85c9ccd4 authored by NeilBrown's avatar NeilBrown Committed by Shaohua Li
Browse files

md/bitmap: Don't write bitmap while earlier writes might be in-flight 



As we don't wait for writes to complete in bitmap_daemon_work, they
could still be in-flight when bitmap_unplug writes again.  Or when
bitmap_daemon_work tries to write again.
This can be confusing and could risk the wrong data being written last.

So make sure we wait for old writes to complete before new writes start.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent a9ae93c8

drivers/md/bitmap.c

+22 −5
Original line number Diff line number Diff line
@@ -416,6 +416,21 @@ out: 
 * bitmap file superblock operations

 */



/*

 * bitmap_wait_writes() should be called before writing any bitmap

 * blocks, to ensure previous writes, particularly from

 * bitmap_daemon_work(), have completed.

 */

static void bitmap_wait_writes(struct bitmap *bitmap)

{

	if (bitmap->storage.file)

		wait_event(bitmap->write_wait,

			   atomic_read(&bitmap->pending_writes)==0);

	else

		md_super_wait(bitmap->mddev);

}





/* update the event counter and sync the superblock to disk */

void bitmap_update_sb(struct bitmap *bitmap)

{
@@ -978,6 +993,7 @@ void bitmap_unplug(struct bitmap *bitmap) 
{

	unsigned long i;

	int dirty, need_write;

	int writing = 0;



	if (!bitmap || !bitmap->storage.filemap ||

	    test_bit(BITMAP_STALE, &bitmap->flags))
@@ -992,15 +1008,15 @@ void bitmap_unplug(struct bitmap *bitmap) 
		need_write = test_and_clear_page_attr(bitmap, i,

						      BITMAP_PAGE_NEEDWRITE);

		if (dirty || need_write) {

			if (!writing)

				bitmap_wait_writes(bitmap);

			clear_page_attr(bitmap, i, BITMAP_PAGE_PENDING);

			write_page(bitmap, bitmap->storage.filemap[i], 0);

			writing = 1;

		}

	}

	if (bitmap->storage.file)

		wait_event(bitmap->write_wait,

			   atomic_read(&bitmap->pending_writes)==0);

	else

		md_super_wait(bitmap->mddev);

	if (writing)

		bitmap_wait_writes(bitmap);



	if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))

		bitmap_file_kick(bitmap);
@@ -1282,6 +1298,7 @@ void bitmap_daemon_work(struct mddev *mddev) 
	}

	spin_unlock_irq(&counts->lock);



	bitmap_wait_writes(bitmap);

	/* Now start writeout on any page in NEEDWRITE that isn't DIRTY.

	 * DIRTY pages need to be written by bitmap_unplug so it can wait

	 * for them.

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