From: Zi Yan <ziy@xxxxxxxxxx>
Users can use the syscall to exchange two lists of pages, similar
to move_pages() syscall.
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
include/linux/syscalls.h | 5 +
mm/exchange.c | 346 +++++++++++++++++++++++++++++++++
3 files changed, 352 insertions(+)
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 92ee0b4..863a21e 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -343,6 +343,7 @@
332 common statx __x64_sys_statx
333 common io_pgetevents __x64_sys_io_pgetevents
334 common rseq __x64_sys_rseq
+335 common exchange_pages __x64_sys_exchange_pages
# don't use numbers 387 through 423, add new calls after the last
# 'common' entry
424 common pidfd_send_signal __x64_sys_pidfd_send_signal
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index e446806..2c1eb49 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1203,6 +1203,11 @@ asmlinkage long sys_mmap_pgoff(unsigned long addr, unsigned long len,
unsigned long fd, unsigned long pgoff);
asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
+asmlinkage long sys_exchange_pages(pid_t pid, unsigned long nr_pages,
+ const void __user * __user *from_pages,
+ const void __user * __user *to_pages,
+ int __user *status,
+ int flags);
/*
* Not a real system call, but a placeholder for syscalls which are
diff --git a/mm/exchange.c b/mm/exchange.c
index 45c7013..48e344e 100644
--- a/mm/exchange.c
+++ b/mm/exchange.c
@@ -22,6 +22,7 @@
#include <linux/buffer_head.h>
#include <linux/fs.h> /* buffer_migrate_page */
#include <linux/backing-dev.h>
+#include <linux/sched/mm.h>
#include "internal.h"
@@ -1212,3 +1213,348 @@ int exchange_pages_concur(struct list_head *exchange_list,
return nr_failed?-EFAULT:0;
}
+
+static int store_status(int __user *status, int start, int value, int nr)
+{
+ while (nr-- > 0) {
+ if (put_user(value, status + start))
+ return -EFAULT;
+ start++;
+ }
+
+ return 0;
+}
+
+static int do_exchange_page_list(struct mm_struct *mm,
+ struct list_head *from_pagelist, struct list_head *to_pagelist,
+ bool migrate_mt, bool migrate_concur)
+{
+ int err;
+ struct exchange_page_info *one_pair;
+ LIST_HEAD(exchange_page_list);
+
+ while (!list_empty(from_pagelist)) {
+ struct page *from_page, *to_page;
+
+ from_page = list_first_entry_or_null(from_pagelist, struct page, lru);
+ to_page = list_first_entry_or_null(to_pagelist, struct page, lru);
+
+ if (!from_page || !to_page)
+ break;
+
+ one_pair = kzalloc(sizeof(struct exchange_page_info), GFP_ATOMIC);
+ if (!one_pair) {
+ err = -ENOMEM;
+ break;
+ }
+
+ list_del(&from_page->lru);
+ list_del(&to_page->lru);
+
+ one_pair->from_page = from_page;
+ one_pair->to_page = to_page;
+
+ list_add_tail(&one_pair->list, &exchange_page_list);
+ }
+
+ if (migrate_concur)
+ err = exchange_pages_concur(&exchange_page_list,
+ MIGRATE_SYNC | (migrate_mt ? MIGRATE_MT : MIGRATE_SINGLETHREAD),
+ MR_SYSCALL);
+ else
+ err = exchange_pages(&exchange_page_list,
+ MIGRATE_SYNC | (migrate_mt ? MIGRATE_MT : MIGRATE_SINGLETHREAD),
+ MR_SYSCALL);
+
+ while (!list_empty(&exchange_page_list)) {
+ struct exchange_page_info *one_pair =
+ list_first_entry(&exchange_page_list,
+ struct exchange_page_info, list);
+
+ list_del(&one_pair->list);
+ kfree(one_pair);
+ }
+
+ if (!list_empty(from_pagelist))
+ putback_movable_pages(from_pagelist);
+
+ if (!list_empty(to_pagelist))
+ putback_movable_pages(to_pagelist);
+
+ return err;
+}
+
+static int add_page_for_exchange(struct mm_struct *mm,
+ unsigned long from_addr, unsigned long to_addr,
+ struct list_head *from_pagelist, struct list_head *to_pagelist,
+ bool migrate_all)
+{
+ struct vm_area_struct *from_vma, *to_vma;
+ struct page *from_page, *to_page;
+ LIST_HEAD(err_page_list);
+ unsigned int follflags;
+ int err;
+
+ err = -EFAULT;
+ from_vma = find_vma(mm, from_addr);
+ if (!from_vma || from_addr < from_vma->vm_start ||
+ !vma_migratable(from_vma))
+ goto set_from_status;
+
+ /* FOLL_DUMP to ignore special (like zero) pages */
+ follflags = FOLL_GET | FOLL_DUMP;
+ from_page = follow_page(from_vma, from_addr, follflags);
+
+ err = PTR_ERR(from_page);
+ if (IS_ERR(from_page))
+ goto set_from_status;
+
+ err = -ENOENT;
+ if (!from_page)
+ goto set_from_status;
+
+ err = -EACCES;
+ if (page_mapcount(from_page) > 1 && !migrate_all)
+ goto put_and_set_from_page;
+
+ if (PageHuge(from_page)) {
+ if (PageHead(from_page))
+ if (isolate_huge_page(from_page, &err_page_list)) {
+ err = 0;
+ }
+ goto put_and_set_from_page;
+ } else if (PageTransCompound(from_page)) {
+ if (PageTail(from_page)) {
+ err = -EACCES;
+ goto put_and_set_from_page;
+ }
+ }
+
+ err = isolate_lru_page(from_page);
+ if (!err)
+ mod_node_page_state(page_pgdat(from_page), NR_ISOLATED_ANON +
+ page_is_file_cache(from_page), hpage_nr_pages(from_page));
+put_and_set_from_page:
+ /*
+ * Either remove the duplicate refcount from
+ * isolate_lru_page() or drop the page ref if it was
+ * not isolated.
+ *
+ * Since FOLL_GET calls get_page(), and isolate_lru_page()
+ * also calls get_page()
+ */
+ put_page(from_page);
+set_from_status:
+ if (err)
+ goto out;
+
+ /* to pages */
+ err = -EFAULT;
+ to_vma = find_vma(mm, to_addr);
+ if (!to_vma ||
+ to_addr < to_vma->vm_start ||
+ !vma_migratable(to_vma))
+ goto set_to_status;
+
+ /* FOLL_DUMP to ignore special (like zero) pages */
+ to_page = follow_page(to_vma, to_addr, follflags);
+
+ err = PTR_ERR(to_page);
+ if (IS_ERR(to_page))
+ goto set_to_status;
+
+ err = -ENOENT;
+ if (!to_page)
+ goto set_to_status;
+
+ err = -EACCES;
+ if (page_mapcount(to_page) > 1 &&
+ !migrate_all)
+ goto put_and_set_to_page;
+
+ if (PageHuge(to_page)) {
+ if (PageHead(to_page))
+ if (isolate_huge_page(to_page, &err_page_list)) {
+ err = 0;
+ }
+ goto put_and_set_to_page;
+ } else if (PageTransCompound(to_page)) {
+ if (PageTail(to_page)) {
+ err = -EACCES;
+ goto put_and_set_to_page;
+ }
+ }
+
+ err = isolate_lru_page(to_page);
+ if (!err)
+ mod_node_page_state(page_pgdat(to_page), NR_ISOLATED_ANON +
+ page_is_file_cache(to_page), hpage_nr_pages(to_page));
+put_and_set_to_page:
+ /*
+ * Either remove the duplicate refcount from
+ * isolate_lru_page() or drop the page ref if it was
+ * not isolated.
+ *
+ * Since FOLL_GET calls get_page(), and isolate_lru_page()
+ * also calls get_page()
+ */
+ put_page(to_page);
+set_to_status:
+ if (!err) {
+ if ((PageHuge(from_page) != PageHuge(to_page)) ||
+ (PageTransHuge(from_page) != PageTransHuge(to_page))) {
+ list_add(&from_page->lru, &err_page_list);
+ list_add(&to_page->lru, &err_page_list);
+ } else {
+ list_add_tail(&from_page->lru, from_pagelist);
+ list_add_tail(&to_page->lru, to_pagelist);
+ }
+ } else
+ list_add(&from_page->lru, &err_page_list);
+out:
+ if (!list_empty(&err_page_list))
+ putback_movable_pages(&err_page_list);
+ return err;
+}
+/*
+ * Migrate an array of page address onto an array of nodes and fill
+ * the corresponding array of status.
+ */
+static int do_pages_exchange(struct mm_struct *mm, nodemask_t task_nodes,
+ unsigned long nr_pages,
+ const void __user * __user *from_pages,
+ const void __user * __user *to_pages,
+ int __user *status, int flags)
+{
+ LIST_HEAD(from_pagelist);
+ LIST_HEAD(to_pagelist);
+ int start, i;
+ int err = 0, err1;
+
+ migrate_prep();
+
+ down_read(&mm->mmap_sem);
+ for (i = start = 0; i < nr_pages; i++) {
+ const void __user *from_p, *to_p;
+ unsigned long from_addr, to_addr;
+
+ err = -EFAULT;
+ if (get_user(from_p, from_pages + i))
+ goto out_flush;
+ if (get_user(to_p, to_pages + i))
+ goto out_flush;
+
+ from_addr = (unsigned long)from_p;
+ to_addr = (unsigned long)to_p;
+
+ err = -EACCES;
+ /*
+ * Errors in the page lookup or isolation are not fatal and we simply
+ * report them via status
+ */
+ err = add_page_for_exchange(mm, from_addr, to_addr,
+ &from_pagelist, &to_pagelist,
+ flags & MPOL_MF_MOVE_ALL);
+
+ if (!err)
+ continue;
+
+ err = store_status(status, i, err, 1);
+ if (err)
+ goto out_flush;
+
+ err = do_exchange_page_list(mm, &from_pagelist, &to_pagelist,
+ flags & MPOL_MF_MOVE_MT,
+ flags & MPOL_MF_MOVE_CONCUR);
+ if (err)
+ goto out;
+ if (i > start) {
+ err = store_status(status, start, 0, i - start);
+ if (err)
+ goto out;
+ }
+ start = i;
+ }
+out_flush:
+ /* Make sure we do not overwrite the existing error */
+ err1 = do_exchange_page_list(mm, &from_pagelist, &to_pagelist,
+ flags & MPOL_MF_MOVE_MT,
+ flags & MPOL_MF_MOVE_CONCUR);
+ if (!err1)
+ err1 = store_status(status, start, 0, i - start);
+ if (!err)
+ err = err1;
+out:
+ up_read(&mm->mmap_sem);
+ return err;
+}
+
+SYSCALL_DEFINE6(exchange_pages, pid_t, pid, unsigned long, nr_pages,
+ const void __user * __user *, from_pages,
+ const void __user * __user *, to_pages,
+ int __user *, status, int, flags)
+{
+ const struct cred *cred = current_cred(), *tcred;
+ struct task_struct *task;
+ struct mm_struct *mm;
+ int err;
+ nodemask_t task_nodes;
+
+ /* Check flags */
+ if (flags & ~(MPOL_MF_MOVE|
+ MPOL_MF_MOVE_ALL|
+ MPOL_MF_MOVE_MT|
+ MPOL_MF_MOVE_CONCUR))
+ return -EINVAL;
+
+ if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
+ return -EPERM;
+
+ /* Find the mm_struct */
+ rcu_read_lock();
+ task = pid ? find_task_by_vpid(pid) : current;
+ if (!task) {
+ rcu_read_unlock();
+ return -ESRCH;
+ }
+ get_task_struct(task);
+
+ /*
+ * Check if this process has the right to modify the specified
+ * process. The right exists if the process has administrative
+ * capabilities, superuser privileges or the same
+ * userid as the target process.
+ */
+ tcred = __task_cred(task);
+ if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
+ !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
+ !capable(CAP_SYS_NICE)) {
+ rcu_read_unlock();
+ err = -EPERM;
+ goto out;
+ }
+ rcu_read_unlock();
+
+ err = security_task_movememory(task);
+ if (err)
+ goto out;
+
+ task_nodes = cpuset_mems_allowed(task);
+ mm = get_task_mm(task);
+ put_task_struct(task);
+
+ if (!mm)
+ return -EINVAL;
+
+ err = do_pages_exchange(mm, task_nodes, nr_pages, from_pages,
+ to_pages, status, flags);
+
+ mmput(mm);
+
+ return err;
+
+out:
+ put_task_struct(task);
+
+ return err;
+}
--
2.7.4
