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Commit 36c9ea98 authored by Kent Overstreet's avatar Kent Overstreet Committed by Kent Overstreet
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bcache: Document shrinker reserve better 



Signed-off-by: default avatarKent Overstreet <kmo@daterainc.com>
parent e49c7c37

drivers/md/bcache/btree.c

+7 −0
Original line number Diff line number Diff line
@@ -622,6 +622,13 @@ static int bch_mca_shrink(struct shrinker *shrink, struct shrink_control *sc) 
	else if (!mutex_trylock(&c->bucket_lock))

		return -1;



	/*

	 * It's _really_ critical that we don't free too many btree nodes - we

	 * have to always leave ourselves a reserve. The reserve is how we

	 * guarantee that allocating memory for a new btree node can always

	 * succeed, so that inserting keys into the btree can always succeed and

	 * IO can always make forward progress:

	 */

	nr /= c->btree_pages;

	nr = min_t(unsigned long, nr, mca_can_free(c));