zcache_do_preload() currently does a spin_trylock() on the zcache_direct_reclaim_lock. Holding this lock intends to prevent shrink_zcache_memory() from evicting zbud pages as a result of a preload.
However, it also prevents two threads from executing zcache_do_preload() at the same time. The first thread will obtain the lock and the second thread's spin_trylock() will fail (an aborted preload) causing the page to be either lost (cleancache) or pushed out to the swap device (frontswap). It also doesn't ensure that the call to shrink_zcache_memory() is on the same thread as the call to zcache_do_preload(). Additional, there is no need for this mechanism because all zcache_do_preload() calls that come down from cleancache already have PF_MEMALLOC set in the process flags which prevents direct reclaim in the memory manager. If the zcache_do_preload() call is done from the frontswap path, we _want_ reclaim to be done (which it isn't right now). This patch removes the zcache_direct_reclaim_lock and related statistics in zcache. Based on v3.1-rc8 Signed-off-by: Seth Jennings <[email protected]> Reviewed-by: Dave Hansen <[email protected]> Acked-by: Dan Magenheimer <[email protected]> --- drivers/staging/zcache/zcache-main.c | 33 ++++++--------------------------- 1 files changed, 6 insertions(+), 27 deletions(-) diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c index 462fbc2..995523f 100644 --- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -962,15 +962,6 @@ out: static unsigned long zcache_failed_get_free_pages; static unsigned long zcache_failed_alloc; static unsigned long zcache_put_to_flush; -static unsigned long zcache_aborted_preload; -static unsigned long zcache_aborted_shrink; - -/* - * Ensure that memory allocation requests in zcache don't result - * in direct reclaim requests via the shrinker, which would cause - * an infinite loop. Maybe a GFP flag would be better? - */ -static DEFINE_SPINLOCK(zcache_direct_reclaim_lock); /* * for now, used named slabs so can easily track usage; later can @@ -1005,14 +996,12 @@ static int zcache_do_preload(struct tmem_pool *pool) void *page; int ret = -ENOMEM; + /* ensure no recursion due to direct reclaim */ + BUG_ON(is_ephemeral(pool) && !(current->flags & PF_MEMALLOC)); if (unlikely(zcache_objnode_cache == NULL)) goto out; if (unlikely(zcache_obj_cache == NULL)) goto out; - if (!spin_trylock(&zcache_direct_reclaim_lock)) { - zcache_aborted_preload++; - goto out; - } preempt_disable(); kp = &__get_cpu_var(zcache_preloads); while (kp->nr < ARRAY_SIZE(kp->objnodes)) { @@ -1021,7 +1010,7 @@ static int zcache_do_preload(struct tmem_pool *pool) ZCACHE_GFP_MASK); if (unlikely(objnode == NULL)) { zcache_failed_alloc++; - goto unlock_out; + goto out; } preempt_disable(); kp = &__get_cpu_var(zcache_preloads); @@ -1034,13 +1023,13 @@ static int zcache_do_preload(struct tmem_pool *pool) obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK); if (unlikely(obj == NULL)) { zcache_failed_alloc++; - goto unlock_out; + goto out; } page = (void *)__get_free_page(ZCACHE_GFP_MASK); if (unlikely(page == NULL)) { zcache_failed_get_free_pages++; kmem_cache_free(zcache_obj_cache, obj); - goto unlock_out; + goto out; } preempt_disable(); kp = &__get_cpu_var(zcache_preloads); @@ -1053,8 +1042,6 @@ static int zcache_do_preload(struct tmem_pool *pool) else free_page((unsigned long)page); ret = 0; -unlock_out: - spin_unlock(&zcache_direct_reclaim_lock); out: return ret; } @@ -1423,8 +1410,6 @@ ZCACHE_SYSFS_RO(evicted_buddied_pages); ZCACHE_SYSFS_RO(failed_get_free_pages); ZCACHE_SYSFS_RO(failed_alloc); ZCACHE_SYSFS_RO(put_to_flush); -ZCACHE_SYSFS_RO(aborted_preload); -ZCACHE_SYSFS_RO(aborted_shrink); ZCACHE_SYSFS_RO(compress_poor); ZCACHE_SYSFS_RO(mean_compress_poor); ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_raw_pages); @@ -1466,8 +1451,6 @@ static struct attribute *zcache_attrs[] = { &zcache_failed_get_free_pages_attr.attr, &zcache_failed_alloc_attr.attr, &zcache_put_to_flush_attr.attr, - &zcache_aborted_preload_attr.attr, - &zcache_aborted_shrink_attr.attr, &zcache_zbud_unbuddied_list_counts_attr.attr, &zcache_zbud_cumul_chunk_counts_attr.attr, &zcache_zv_curr_dist_counts_attr.attr, @@ -1507,11 +1490,7 @@ static int shrink_zcache_memory(struct shrinker *shrink, if (!(gfp_mask & __GFP_FS)) /* does this case really need to be skipped? */ goto out; - if (spin_trylock(&zcache_direct_reclaim_lock)) { - zbud_evict_pages(nr); - spin_unlock(&zcache_direct_reclaim_lock); - } else - zcache_aborted_shrink++; + zbud_evict_pages(nr); } ret = (int)atomic_read(&zcache_zbud_curr_raw_pages); out: -- 1.7.4.1 _______________________________________________ devel mailing list [email protected] http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
