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Date: Tue, 27 Feb 2018 08:25:48 +0800
From: Yang Shi <yang.shi@...ux.alibaba.com>
To: akpm@...ux-foundation.org, mingo@...nel.org, adobriyan@...il.com
Cc: yang.shi@...ux.alibaba.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/4 v2] mm: add access_remote_vm_killable APIs
Extracted common part (without acquiring mmap_sem) of
__access_remote_vm() into raw_access_remote_vm() then create
__access_remote_vm_killable() and access_remote_vm_killable() with
acquiring mmap_sem by down_read_killable().
Keep non-killable versions using down_read().
The killable version will be used by reading /proc/*/cmdline and
/proc/*/environ for the time being.
Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>
---
include/linux/mm.h | 5 +++++
mm/memory.c | 44 +++++++++++++++++++++++++++++++++++++-------
mm/nommu.c | 36 ++++++++++++++++++++++++++++++++----
3 files changed, 74 insertions(+), 11 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ad06d42..4574b19 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1372,8 +1372,13 @@ extern int access_process_vm(struct task_struct *tsk, unsigned long addr,
void *buf, int len, unsigned int gup_flags);
extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, unsigned int gup_flags);
+extern int access_remote_vm_killable(struct mm_struct *mm, unsigned long addr,
+ void *buf, int len, unsigned int gup_flags);
extern int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
unsigned long addr, void *buf, int len, unsigned int gup_flags);
+extern int __access_remote_vm_killable(struct task_struct *tsk,
+ struct mm_struct *mm, unsigned long addr, void *buf, int len,
+ unsigned int gup_flags);
long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
diff --git a/mm/memory.c b/mm/memory.c
index dd8de96..8d7e223 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4415,18 +4415,13 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
EXPORT_SYMBOL_GPL(generic_access_phys);
#endif
-/*
- * Access another process' address space as given in mm. If non-NULL, use the
- * given task for page fault accounting.
- */
-int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+static int raw_access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
unsigned long addr, void *buf, int len, unsigned int gup_flags)
{
struct vm_area_struct *vma;
void *old_buf = buf;
int write = gup_flags & FOLL_WRITE;
- down_read(&mm->mmap_sem);
/* ignore errors, just check how much was successfully transferred */
while (len) {
int bytes, ret, offset;
@@ -4475,11 +4470,40 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
buf += bytes;
addr += bytes;
}
- up_read(&mm->mmap_sem);
return buf - old_buf;
}
+/*
+ * Access another process' address space as given in mm. If non-NULL, use the
+ * given task for page fault accounting.
+ */
+int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long addr, void *buf, int len, unsigned int gup_flags)
+{
+ int ret;
+
+ down_read(&mm->mmap_sem);
+ ret = raw_access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
+ up_read(&mm->mmap_sem);
+ return ret;
+}
+
+int __access_remote_vm_killable(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long addr, void *buf, int len, unsigned int gup_flags)
+{
+ int ret;
+
+ ret = down_read_killable(&mm->mmap_sem);
+ if (ret)
+ goto out;
+
+ ret = raw_access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
+ up_read(&mm->mmap_sem);
+out:
+ return ret;
+}
+
/**
* access_remote_vm - access another process' address space
* @mm: the mm_struct of the target address space
@@ -4490,6 +4514,12 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
*
* The caller must hold a reference on @mm.
*/
+int access_remote_vm_killable(struct mm_struct *mm, unsigned long addr,
+ void *buf, int len, unsigned int gup_flags)
+{
+ return __access_remote_vm_killable(NULL, mm, addr, buf, len, gup_flags);
+}
+
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, unsigned int gup_flags)
{
diff --git a/mm/nommu.c b/mm/nommu.c
index ebb6e61..ea043b3 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1802,14 +1802,12 @@ void filemap_map_pages(struct vm_fault *vmf,
}
EXPORT_SYMBOL(filemap_map_pages);
-int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+static int raw_access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
unsigned long addr, void *buf, int len, unsigned int gup_flags)
{
struct vm_area_struct *vma;
int write = gup_flags & FOLL_WRITE;
- down_read(&mm->mmap_sem);
-
/* the access must start within one of the target process's mappings */
vma = find_vma(mm, addr);
if (vma) {
@@ -1830,9 +1828,33 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
len = 0;
}
+ return len;
+}
+
+int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long addr, void *buf, int len, unsigned int gup_flags)
+{
+ int ret;
+
+ down_read(&mm->mmap_sem);
+ ret = raw_access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
up_read(&mm->mmap_sem);
+ return ret;
+}
- return len;
+int __access_remote_vm_killable(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long addr, void *buf, int len, unsigned int gup_flags)
+{
+ int ret;
+
+ ret = down_read_killable(&mm->mmap_sem);
+ if (ret)
+ goto out;
+
+ ret = raw_access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
+ up_read(&mm->mmap_sem);
+out:
+ return ret;
}
/**
@@ -1845,6 +1867,12 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
*
* The caller must hold a reference on @mm.
*/
+int access_remote_vm_killable(struct mm_struct *mm, unsigned long addr,
+ void *buf, int len, unsigned int gup_flags)
+{
+ return __access_remote_vm_killable(NULL, mm, addr, buf, len, gup_flags);
+}
+
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, unsigned int gup_flags)
{
--
1.8.3.1
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