The patch titled
splice: use get_user_pages_fast
has been added to the -mm tree. Its filename is
splice-use-get_user_pages_fast.patch
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------------------------------------------------------
Subject: splice: use get_user_pages_fast
From: Nick Piggin <npiggin@xxxxxxx>
Use get_user_pages_fast in splice. This reverts some mmap_sem batching
there, however the biggest problem with mmap_sem tends to be hold times
blocking out other threads rather than cacheline bouncing. Further: on
architectures that implement get_user_pages_fast without locks, mmap_sem
can be avoided completely anyway.
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Cc: Dave Kleikamp <shaggy@xxxxxxxxxxxxxx>
Cc: Andy Whitcroft <apw@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Dave Kleikamp <shaggy@xxxxxxxxxxxxxx>
Cc: Badari Pulavarty <pbadari@xxxxxxxxxx>
Cc: Zach Brown <zach.brown@xxxxxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/splice.c | 41 +++--------------------------------------
1 file changed, 3 insertions(+), 38 deletions(-)
diff -puN fs/splice.c~splice-use-get_user_pages_fast fs/splice.c
--- a/fs/splice.c~splice-use-get_user_pages_fast
+++ a/fs/splice.c
@@ -1154,36 +1154,6 @@ static long do_splice(struct file *in, l
}
/*
- * Do a copy-from-user while holding the mmap_semaphore for reading, in a
- * manner safe from deadlocking with simultaneous mmap() (grabbing mmap_sem
- * for writing) and page faulting on the user memory pointed to by src.
- * This assumes that we will very rarely hit the partial != 0 path, or this
- * will not be a win.
- */
-static int copy_from_user_mmap_sem(void *dst, const void __user *src, size_t n)
-{
- int partial;
-
- if (!access_ok(VERIFY_READ, src, n))
- return -EFAULT;
-
- pagefault_disable();
- partial = __copy_from_user_inatomic(dst, src, n);
- pagefault_enable();
-
- /*
- * Didn't copy everything, drop the mmap_sem and do a faulting copy
- */
- if (unlikely(partial)) {
- up_read(¤t->mm->mmap_sem);
- partial = copy_from_user(dst, src, n);
- down_read(¤t->mm->mmap_sem);
- }
-
- return partial;
-}
-
-/*
* Map an iov into an array of pages and offset/length tupples. With the
* partial_page structure, we can map several non-contiguous ranges into
* our ones pages[] map instead of splitting that operation into pieces.
@@ -1196,8 +1166,6 @@ static int get_iovec_page_array(const st
{
int buffers = 0, error = 0;
- down_read(¤t->mm->mmap_sem);
-
while (nr_vecs) {
unsigned long off, npages;
struct iovec entry;
@@ -1206,7 +1174,7 @@ static int get_iovec_page_array(const st
int i;
error = -EFAULT;
- if (copy_from_user_mmap_sem(&entry, iov, sizeof(entry)))
+ if (copy_from_user(&entry, iov, sizeof(entry)))
break;
base = entry.iov_base;
@@ -1240,9 +1208,8 @@ static int get_iovec_page_array(const st
if (npages > PIPE_BUFFERS - buffers)
npages = PIPE_BUFFERS - buffers;
- error = get_user_pages(current, current->mm,
- (unsigned long) base, npages, 0, 0,
- &pages[buffers], NULL);
+ error = get_user_pages_fast((unsigned long)base, npages,
+ 0, &pages[buffers]);
if (unlikely(error <= 0))
break;
@@ -1281,8 +1248,6 @@ static int get_iovec_page_array(const st
iov++;
}
- up_read(¤t->mm->mmap_sem);
-
if (buffers)
return buffers;
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
hugetlb-fix-lockdep-error.patch
linux-next.patch
spufs-convert-nopfn-to-fault.patch
vt-fix-vc_resize-locking.patch
mspec-convert-nopfn-to-fault.patch
mspec-convert-nopfn-to-fault-fix.patch
mm-remove-nopfn.patch
mm-remove-double-indirection-on-tlb-parameter-to-free_pgd_range-co.patch
x86-implement-pte_special.patch
mm-introduce-get_user_pages_fast.patch
mm-introduce-get_user_pages_fast-checkpatch-fixes.patch
x86-lockless-get_user_pages_fast.patch
x86-lockless-get_user_pages_fast-checkpatch-fixes.patch
x86-lockless-get_user_pages_fast-fix.patch
x86-lockless-get_user_pages_fast-fix-warning.patch
dio-use-get_user_pages_fast.patch
splice-use-get_user_pages_fast.patch
reiser4.patch
likeliness-accounting-change-and-cleanup.patch
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