The get_user_pages_locked() function is needed by the frame vector code
which will be added in the next patch. While adding that, this patch
also replaces the get_user_pages_unlocked() function with the original
version from the next kernel.
Signed-off-by: Hauke Mehrtens <hauke@xxxxxxxxxx>
---
backport/backport-include/linux/mm.h | 30 +++---
backport/compat/Makefile | 1 +
backport/compat/backport-4.0.c | 193 +++++++++++++++++++++++++++++++++++
3 files changed, 211 insertions(+), 13 deletions(-)
create mode 100644 backport/compat/backport-4.0.c
diff --git a/backport/backport-include/linux/mm.h b/backport/backport-include/linux/mm.h
index d6cbffe..f9e0ced 100644
--- a/backport/backport-include/linux/mm.h
+++ b/backport/backport-include/linux/mm.h
@@ -31,20 +31,24 @@ void kvfree(const void *addr);
#endif /* < 3.15 */
#if (LINUX_VERSION_CODE < KERNEL_VERSION(3,20,0))
+#define get_user_pages_locked LINUX_BACKPORT(get_user_pages_locked)
+long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ int write, int force, struct page **pages,
+ int *locked);
+#define __get_user_pages_unlocked LINUX_BACKPORT(__get_user_pages_unlocked)
+long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ int write, int force, struct page **pages,
+ unsigned int gup_flags);
#define get_user_pages_unlocked LINUX_BACKPORT(get_user_pages_unlocked)
-static inline long
-get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, unsigned long nr_pages,
- int write, int force, struct page **pages)
-{
- long err;
-
- down_read(&mm->mmap_sem);
- err = get_user_pages(tsk, mm, start, nr_pages, write, force, pages,
- NULL);
- up_read(&mm->mmap_sem);
+long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ int write, int force, struct page **pages);
+#endif
- return err;
-}
+#ifndef FOLL_TRIED
+#define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
#endif
+
#endif /* __BACKPORT_MM_H */
diff --git a/backport/compat/Makefile b/backport/compat/Makefile
index d0acf17..23c0713 100644
--- a/backport/compat/Makefile
+++ b/backport/compat/Makefile
@@ -25,6 +25,7 @@ compat-$(CPTCFG_KERNEL_3_15) += backport-3.15.o
compat-$(CPTCFG_KERNEL_3_17) += backport-3.17.o
compat-$(CPTCFG_KERNEL_3_18) += backport-3.18.o
compat-$(CPTCFG_KERNEL_3_19) += backport-3.19.o
+compat-$(CPTCFG_KERNEL_4_0) += backport-4.0.o
compat-$(CPTCFG_KERNEL_4_1) += backport-4.1.o
compat-$(CPTCFG_KERNEL_4_2) += backport-4.2.o
diff --git a/backport/compat/backport-4.0.c b/backport/compat/backport-4.0.c
new file mode 100644
index 0000000..3de1211
--- /dev/null
+++ b/backport/compat/backport-4.0.c
@@ -0,0 +1,193 @@
+/*
+ * Copyright (c) 2015 Hauke Mehrtens <hauke@xxxxxxxxxx>
+ *
+ * Backport functionality introduced in Linux 4.0.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/export.h>
+
+static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
+ struct mm_struct *mm,
+ unsigned long start,
+ unsigned long nr_pages,
+ int write, int force,
+ struct page **pages,
+ struct vm_area_struct **vmas,
+ int *locked, bool notify_drop,
+ unsigned int flags)
+{
+ long ret, pages_done;
+ bool lock_dropped;
+
+ if (locked) {
+ /* if VM_FAULT_RETRY can be returned, vmas become invalid */
+ BUG_ON(vmas);
+ /* check caller initialized locked */
+ BUG_ON(*locked != 1);
+ }
+
+ if (pages)
+ flags |= FOLL_GET;
+ if (write)
+ flags |= FOLL_WRITE;
+ if (force)
+ flags |= FOLL_FORCE;
+
+ pages_done = 0;
+ lock_dropped = false;
+ for (;;) {
+ ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
+ vmas, locked);
+ if (!locked)
+ /* VM_FAULT_RETRY couldn't trigger, bypass */
+ return ret;
+
+ /* VM_FAULT_RETRY cannot return errors */
+ if (!*locked) {
+ BUG_ON(ret < 0);
+ BUG_ON(ret >= nr_pages);
+ }
+
+ if (!pages)
+ /* If it's a prefault don't insist harder */
+ return ret;
+
+ if (ret > 0) {
+ nr_pages -= ret;
+ pages_done += ret;
+ if (!nr_pages)
+ break;
+ }
+ if (*locked) {
+ /* VM_FAULT_RETRY didn't trigger */
+ if (!pages_done)
+ pages_done = ret;
+ break;
+ }
+ /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
+ pages += ret;
+ start += ret << PAGE_SHIFT;
+
+ /*
+ * Repeat on the address that fired VM_FAULT_RETRY
+ * without FAULT_FLAG_ALLOW_RETRY but with
+ * FAULT_FLAG_TRIED.
+ */
+ *locked = 1;
+ lock_dropped = true;
+ down_read(&mm->mmap_sem);
+ ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
+ pages, NULL, NULL);
+ if (ret != 1) {
+ BUG_ON(ret > 1);
+ if (!pages_done)
+ pages_done = ret;
+ break;
+ }
+ nr_pages--;
+ pages_done++;
+ if (!nr_pages)
+ break;
+ pages++;
+ start += PAGE_SIZE;
+ }
+ if (notify_drop && lock_dropped && *locked) {
+ /*
+ * We must let the caller know we temporarily dropped the lock
+ * and so the critical section protected by it was lost.
+ */
+ up_read(&mm->mmap_sem);
+ *locked = 0;
+ }
+ return pages_done;
+}
+
+/*
+ * We can leverage the VM_FAULT_RETRY functionality in the page fault
+ * paths better by using either get_user_pages_locked() or
+ * get_user_pages_unlocked().
+ *
+ * get_user_pages_locked() is suitable to replace the form:
+ *
+ * down_read(&mm->mmap_sem);
+ * do_something()
+ * get_user_pages(tsk, mm, ..., pages, NULL);
+ * up_read(&mm->mmap_sem);
+ *
+ * to:
+ *
+ * int locked = 1;
+ * down_read(&mm->mmap_sem);
+ * do_something()
+ * get_user_pages_locked(tsk, mm, ..., pages, &locked);
+ * if (locked)
+ * up_read(&mm->mmap_sem);
+ */
+long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ int write, int force, struct page **pages,
+ int *locked)
+{
+ return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
+ pages, NULL, locked, true, FOLL_TOUCH);
+}
+EXPORT_SYMBOL_GPL(get_user_pages_locked);
+
+/*
+ * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to
+ * pass additional gup_flags as last parameter (like FOLL_HWPOISON).
+ *
+ * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
+ * caller if required (just like with __get_user_pages). "FOLL_GET",
+ * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed
+ * according to the parameters "pages", "write", "force"
+ * respectively.
+ */
+__always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ int write, int force, struct page **pages,
+ unsigned int gup_flags)
+{
+ long ret;
+ int locked = 1;
+ down_read(&mm->mmap_sem);
+ ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
+ pages, NULL, &locked, false, gup_flags);
+ if (locked)
+ up_read(&mm->mmap_sem);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(__get_user_pages_unlocked);
+
+/*
+ * get_user_pages_unlocked() is suitable to replace the form:
+ *
+ * down_read(&mm->mmap_sem);
+ * get_user_pages(tsk, mm, ..., pages, NULL);
+ * up_read(&mm->mmap_sem);
+ *
+ * with:
+ *
+ * get_user_pages_unlocked(tsk, mm, ..., pages);
+ *
+ * It is functionally equivalent to get_user_pages_fast so
+ * get_user_pages_fast should be used instead, if the two parameters
+ * "tsk" and "mm" are respectively equal to current and current->mm,
+ * or if "force" shall be set to 1 (get_user_pages_fast misses the
+ * "force" parameter).
+ */
+long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ int write, int force, struct page **pages)
+{
+ return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write,
+ force, pages, FOLL_TOUCH);
+}
+EXPORT_SYMBOL_GPL(get_user_pages_unlocked);
--
2.1.4
--
To unsubscribe from this list: send the line "unsubscribe backports" in
