Re: [PATCH 07/19] mm/gup: introduce pin_user_pages*() and FOLL_PIN
On 11/25/19 12:44 AM, kbuild test robot wrote: > Hi John, > > Thank you for the patch! Yet something to improve: > > [auto build test ERROR on rdma/for-next] > [cannot apply to v5.4 next-20191122] > [if your patch is applied to the wrong git tree, please drop us a note to help > improve the system. BTW, we also suggest to use '--base' option to specify the > base tree in git format-patch, please see > https://stackoverflow.com/a/37406982] > > url: > https://github.com/0day-ci/linux/commits/John-Hubbard/pin_user_pages-reduced-risk-series-for-Linux-5-5/20191125-125637 > base: https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git for-next > config: arm-randconfig-a001-20191125 (attached as .config) > compiler: arm-linux-gnueabi-gcc (GCC) 7.4.0 > reproduce: > wget > https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O > ~/bin/make.cross > chmod +x ~/bin/make.cross > # save the attached .config to linux build tree > GCC_VERSION=7.4.0 make.cross ARCH=arm > > If you fix the issue, kindly add following tag > Reported-by: kbuild test robot > > All errors (new ones prefixed by >>): > >mm/gup.o: In function `pin_user_pages_remote': >>> mm/gup.c:2528: undefined reference to `get_user_pages_remote' > > vim +2528 mm/gup.c This, and the other (sh) report, is due to !CONFIG_MMU lacking a get_user_pages_remote(), but pin_user_pages_remote() needs it for a (temporary) implementation. I'll post the fix, in v2. thanks, -- John Hubbard NVIDIA
Re: [PATCH 07/19] mm/gup: introduce pin_user_pages*() and FOLL_PIN
Hi John,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on rdma/for-next]
[cannot apply to v5.4 next-20191122]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
url:
https://github.com/0day-ci/linux/commits/John-Hubbard/pin_user_pages-reduced-risk-series-for-Linux-5-5/20191125-125637
base: https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git for-next
config: arm-randconfig-a001-20191125 (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 7.4.0
reproduce:
wget
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
GCC_VERSION=7.4.0 make.cross ARCH=arm
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot
All errors (new ones prefixed by >>):
mm/gup.o: In function `pin_user_pages_remote':
>> mm/gup.c:2528: undefined reference to `get_user_pages_remote'
vim +2528 mm/gup.c
2507
2508 /**
2509 * pin_user_pages_remote() - pin pages of a remote process (task !=
current)
2510 *
2511 * For now, this is a placeholder function, until various call sites are
2512 * converted to use the correct get_user_pages*() or pin_user_pages*()
API. So,
2513 * this is identical to get_user_pages_remote().
2514 *
2515 * This is intended for Case 1 (DIO) in
Documentation/vm/pin_user_pages.rst. It
2516 * is NOT intended for Case 2 (RDMA: long-term pins).
2517 */
2518 long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct
*mm,
2519 unsigned long start, unsigned long nr_pages,
2520 unsigned int gup_flags, struct page **pages,
2521 struct vm_area_struct **vmas, int *locked)
2522 {
2523 /*
2524 * This is a placeholder, until the pin functionality is
activated.
2525 * Until then, just behave like the corresponding
get_user_pages*()
2526 * routine.
2527 */
> 2528 return get_user_pages_remote(tsk, mm, start, nr_pages,
> gup_flags, pages,
2529 vmas, locked);
2530 }
2531 EXPORT_SYMBOL(pin_user_pages_remote);
2532
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/hyperkitty/list/kbuild-...@lists.01.org Intel Corporation
.config.gz
Description: application/gzip
Re: [PATCH 07/19] mm/gup: introduce pin_user_pages*() and FOLL_PIN
Hi John, Thank you for the patch! Yet something to improve: [auto build test ERROR on rdma/for-next] [also build test ERROR on v5.4 next-20191122] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system. BTW, we also suggest to use '--base' option to specify the base tree in git format-patch, please see https://stackoverflow.com/a/37406982] url: https://github.com/0day-ci/linux/commits/John-Hubbard/pin_user_pages-reduced-risk-series-for-Linux-5-5/20191125-125637 base: https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git for-next config: sh-rsk7269_defconfig (attached as .config) compiler: sh4-linux-gcc (GCC) 7.4.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree GCC_VERSION=7.4.0 make.cross ARCH=sh If you fix the issue, kindly add following tag Reported-by: kbuild test robot All errors (new ones prefixed by >>): mm/gup.o: In function `pin_user_pages_remote': >> gup.c:(.text+0x4a4): undefined reference to `get_user_pages_remote' --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/hyperkitty/list/kbuild-...@lists.01.org Intel Corporation .config.gz Description: application/gzip
[PATCH 07/19] mm/gup: introduce pin_user_pages*() and FOLL_PIN
Introduce pin_user_pages*() variations of get_user_pages*() calls,
and also pin_longterm_pages*() variations.
For now, these are placeholder calls, until the various call sites
are converted to use the correct get_user_pages*() or
pin_user_pages*() API.
These variants will eventually all set FOLL_PIN, which is also
introduced, and thoroughly documented.
pin_user_pages()
pin_user_pages_remote()
pin_user_pages_fast()
All pages that are pinned via the above calls, must be unpinned via
put_user_page().
The underlying rules are:
* FOLL_PIN is a gup-internal flag, so the call sites should not directly
set it. That behavior is enforced with assertions.
* Call sites that want to indicate that they are going to do DirectIO
("DIO") or something with similar characteristics, should call a
get_user_pages()-like wrapper call that sets FOLL_PIN. These wrappers
will:
* Start with "pin_user_pages" instead of "get_user_pages". That
makes it easy to find and audit the call sites.
* Set FOLL_PIN
* For pages that are received via FOLL_PIN, those pages must be returned
via put_user_page().
Thanks to Jan Kara and Vlastimil Babka for explaining the 4 cases
in this documentation. (I've reworded it and expanded upon it.)
Reviewed-by: Jan Kara
Reviewed-by: Mike Rapoport # Documentation
Reviewed-by: Jérôme Glisse
Cc: Jonathan Corbet
Cc: Ira Weiny
Signed-off-by: John Hubbard
---
Documentation/core-api/index.rst | 1 +
Documentation/core-api/pin_user_pages.rst | 233 ++
include/linux/mm.h| 63 --
mm/gup.c | 153 --
4 files changed, 416 insertions(+), 34 deletions(-)
create mode 100644 Documentation/core-api/pin_user_pages.rst
diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index ab0eae1c153a..413f7d7c8642 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -31,6 +31,7 @@ Core utilities
generic-radix-tree
memory-allocation
mm-api
+ pin_user_pages
gfp_mask-from-fs-io
timekeeping
boot-time-mm
diff --git a/Documentation/core-api/pin_user_pages.rst
b/Documentation/core-api/pin_user_pages.rst
new file mode 100644
index ..4f26637a5005
--- /dev/null
+++ b/Documentation/core-api/pin_user_pages.rst
@@ -0,0 +1,233 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+
+pin_user_pages() and related calls
+
+
+.. contents:: :local:
+
+Overview
+
+
+This document describes the following functions: ::
+
+ pin_user_pages
+ pin_user_pages_fast
+ pin_user_pages_remote
+
+Basic description of FOLL_PIN
+=
+
+FOLL_PIN and FOLL_LONGTERM are flags that can be passed to the
get_user_pages*()
+("gup") family of functions. FOLL_PIN has significant interactions and
+interdependencies with FOLL_LONGTERM, so both are covered here.
+
+FOLL_PIN is internal to gup, meaning that it should not appear at the gup call
+sites. This allows the associated wrapper functions (pin_user_pages*() and
+others) to set the correct combination of these flags, and to check for
problems
+as well.
+
+FOLL_LONGTERM, on the other hand, *is* allowed to be set at the gup call sites.
+This is in order to avoid creating a large number of wrapper functions to cover
+all combinations of get*(), pin*(), FOLL_LONGTERM, and more. Also, the
+pin_user_pages*() APIs are clearly distinct from the get_user_pages*() APIs, so
+that's a natural dividing line, and a good point to make separate wrapper
calls.
+In other words, use pin_user_pages*() for DMA-pinned pages, and
+get_user_pages*() for other cases. There are four cases described later on in
+this document, to further clarify that concept.
+
+FOLL_PIN and FOLL_GET are mutually exclusive for a given gup call. However,
+multiple threads and call sites are free to pin the same struct pages, via both
+FOLL_PIN and FOLL_GET. It's just the call site that needs to choose one or the
+other, not the struct page(s).
+
+The FOLL_PIN implementation is nearly the same as FOLL_GET, except that
FOLL_PIN
+uses a different reference counting technique.
+
+FOLL_PIN is a prerequisite to FOLL_LONGTGERM. Another way of saying that is,
+FOLL_LONGTERM is a specific case, more restrictive case of FOLL_PIN.
+
+Which flags are set by each wrapper
+===
+
+For these pin_user_pages*() functions, FOLL_PIN is OR'd in with whatever gup
+flags the caller provides. The caller is required to pass in a non-null struct
+pages* array, and the function then pin pages by incrementing each by a special
+value. For now, that value is +1, just like get_user_pages*().::
+
+ Function
+
+ pin_user_pages FOLL_PIN is always set internally by this function.
+ pin_user_pages_fast FOLL_PIN is always set internally by this function.
+
