Messages in this thread | | | Date | Wed, 28 Feb 2018 19:08:21 +0000 | From | "Luis R. Rodriguez" <> | Subject | Re: [PATCH] xfs: Correctly invert xfs_buftarg LRU isolation logic |
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On Wed, Feb 28, 2018 at 04:49:51PM +0100, Vratislav Bendel wrote: > The function xfs_buftarg_isolate() used by xfs buffer schrinkers > to determine whether a buffer should be isolated and disposed > from LRU list, has inverted logic. > > Excerpt from xfs_buftarg_isolate(): > /* > * Decrement the b_lru_ref count unless the value is already > * zero. If the value is already zero, we need to reclaim the > * buffer, otherwise it gets another trip through the LRU. > */ > if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) { > spin_unlock(&bp->b_lock); > return LRU_ROTATE; > } > > However, as per documentation, atomic_add_unless() returns _zero_ > if the atomic value was originally equal to the specified *unsless* value. > > Ultimately causing a xfs_buffer with ->b_lru_ref == 0, to take another > trip around LRU, while isolating buffers with non-zero b_lru_ref. > > Signed-off-by: Vratislav Bendel <vbendel@redhat.com> > CC: Brian Foster <bfoster@redhat.com>
Can you add a respective Fixes: tag? Also what effects are observed by the user when this happens on the kernel log?
Luis
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