[PATCH 1/3] shmem: fix tmpfs to handle the huge= option properly

[PATCH 1/3] shmem: fix tmpfs to handle the huge= option properly

[Hugh Dickins]

From: Toshi Kani <toshi.kani@hpe.com>

shmem_get_unmapped_area() checks SHMEM_SB(sb)->huge incorrectly,
which leads to a reversed effect of "huge=" mount option.

Fix the check in shmem_get_unmapped_area().

Note, the default value of SHMEM_SB(sb)->huge remains as
SHMEM_HUGE_NEVER.  User will need to specify "huge=" option to
enable huge page mappings.

Reported-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
---

 mm/shmem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 4.8-rc7/mm/shmem.c	2016-08-14 20:17:02.388843463 -0700
+++ linux/mm/shmem.c	2016-09-22 19:41:29.057848626 -0700
@@ -1980,7 +1980,7 @@ unsigned long shmem_get_unmapped_area(st
 				return addr;
 			sb = shm_mnt->mnt_sb;
 		}
-		if (SHMEM_SB(sb)->huge != SHMEM_HUGE_NEVER)
+		if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
 			return addr;
 	}
 

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[PATCH 2/3] huge tmpfs: fix Committed_AS leak

[Hugh Dickins]

Under swapping load on huge tmpfs, /proc/meminfo's Committed_AS grows
bigger and bigger: just a cosmetic issue for most users, but disabling
for those who run without overcommit (/proc/sys/vm/overcommit_memory 2).

shmem_uncharge() was forgetting to unaccount __vm_enough_memory's charge,
and shmem_charge() was forgetting it on the filesystem-full error path.

Fixes: 800d8c63b2e9 ("shmem: add huge pages support")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---

 mm/shmem.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 4.8-rc7/mm/shmem.c	2016-08-14 20:17:02.388843463 -0700
+++ linux/mm/shmem.c	2016-09-22 09:29:15.462690346 -0700
@@ -270,7 +270,7 @@ bool shmem_charge(struct inode *inode, l
 		info->alloced -= pages;
 		shmem_recalc_inode(inode);
 		spin_unlock_irqrestore(&info->lock, flags);
-
+		shmem_unacct_blocks(info->flags, pages);
 		return false;
 	}
 	percpu_counter_add(&sbinfo->used_blocks, pages);
@@ -291,6 +291,7 @@ void shmem_uncharge(struct inode *inode,
 
 	if (sbinfo->max_blocks)
 		percpu_counter_sub(&sbinfo->used_blocks, pages);
+	shmem_unacct_blocks(info->flags, pages);
 }
 
 /*

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[PATCH 3/3] mm: delete unnecessary and unsafe init_tlb_ubc()

[Hugh Dickins]

init_tlb_ubc() looked unnecessary to me: tlb_ubc is statically initialized
with zeroes in the init_task, and copied from parent to child while it is
quiescent in arch_dup_task_struct(); so I went to delete it.

But inserted temporary debug WARN_ONs in place of init_tlb_ubc() to check
that it was always empty at that point, and found them firing: because
memcg reclaim can recurse into global reclaim (when allocating biosets
for swapout in my case), and arrive back at the init_tlb_ubc() in
shrink_node_memcg().

Resetting tlb_ubc.flush_required at that point is wrong: if the upper
level needs a deferred TLB flush, but the lower level turns out not to,
we miss a TLB flush.  But fortunately, that's the only part of the
protocol that does not nest: with the initialization removed, cpumask 
collects bits from upper and lower levels, and flushes TLB when needed.

Fixes: 72b252aed506 ("mm: send one IPI per CPU to TLB flush all entries after unmapping pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: stable@vger.kernel.org # 4.3+
---

 mm/vmscan.c |   19 -------------------
 1 file changed, 19 deletions(-)

--- 4.8-rc7/mm/vmscan.c	2016-09-05 16:42:52.496692429 -0700
+++ linux/mm/vmscan.c	2016-09-22 09:32:37.900894833 -0700
@@ -2303,23 +2303,6 @@ out:
 	}
 }
 
-#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
-static void init_tlb_ubc(void)
-{
-	/*
-	 * This deliberately does not clear the cpumask as it's expensive
-	 * and unnecessary. If there happens to be data in there then the
-	 * first SWAP_CLUSTER_MAX pages will send an unnecessary IPI and
-	 * then will be cleared.
-	 */
-	current->tlb_ubc.flush_required = false;
-}
-#else
-static inline void init_tlb_ubc(void)
-{
-}
-#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
-
 /*
  * This is a basic per-node page freer.  Used by both kswapd and direct reclaim.
  */
@@ -2355,8 +2338,6 @@ static void shrink_node_memcg(struct pgl
 	scan_adjusted = (global_reclaim(sc) && !current_is_kswapd() &&
 			 sc->priority == DEF_PRIORITY);
 
-	init_tlb_ubc();
-
 	blk_start_plug(&plug);
 	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
 					nr[LRU_INACTIVE_FILE]) {

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