+ mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     Subject: arch/mips/mm/c-r4k.c: do not use mmap_sem for gup_fast()
has been added to the -mm tree.  Its filename is
     mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch

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------------------------------------------------------
From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: arch/mips/mm/c-r4k.c: do not use mmap_sem for gup_fast()

It is well known that because the mm can internally call the regular
gup_unlocked if the lockless approach fails and take the sem there, the
caller must not hold the mmap_sem already.

Link: http://lkml.kernel.org/r/20190207053740.26915-3-dave@xxxxxxxxxxxx
Fixes: e523f289fe4d ("MIPS: c-r4k: Fix sigtramp SMP call to use kmap")
Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxx>
Cc: James Hogan <jhogan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---


--- a/arch/mips/mm/c-r4k.c~mips-c-r4k-do-no-use-mmap_sem-for-gup_fast
+++ a/arch/mips/mm/c-r4k.c
@@ -1034,11 +1034,9 @@ static void r4k_flush_cache_sigtramp(uns
 	struct flush_cache_sigtramp_args args;
 	int npages;
 
-	down_read(&current->mm->mmap_sem);
-
 	npages = get_user_pages_fast(addr, 1, 0, &args.page);
 	if (npages < 1)
-		goto out;
+		return;
 
 	args.mm = current->mm;
 	args.addr = addr;
@@ -1046,8 +1044,6 @@ static void r4k_flush_cache_sigtramp(uns
 	r4k_on_each_cpu(R4K_HIT, local_r4k_flush_cache_sigtramp, &args);
 
 	put_page(args.page);
-out:
-	up_read(&current->mm->mmap_sem);
 }
 
 static void r4k_flush_icache_all(void)
_

Patches currently in -mm which might be from dave@xxxxxxxxxxxx are

mm-make-mm-pinned_vm-an-atomic64-counter.patch
drivers-mic-scif-do-not-use-mmap_sem.patch
drivers-ibqib-optimize-mmap_sem-usage.patch
drivers-ibhfi1-do-not-se-mmap_sem.patch
drivers-ibusnic-reduce-scope-of-mmap_sem.patch
drivers-ibcore-reduce-scope-of-mmap_sem.patch
xsk-do-not-use-mmap_sem.patch
mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch