[PATCH v6 1/7] mm: pass task and mm to do_madvise

From: Minchan Kim
Date: Tue Feb 18 2020 - 20:44:43 EST

In upcoming patches, do_madvise will be called from external process
context so we shouldn't asssume "current" is always hinted process's
task_struct. Furthermore, we couldn't access mm_struct via task->mm
once it's verified by access_mm which will be introduced in next
patch[1]. And let's pass *current* and current->mm as arguments of
do_madvise so it shouldn't change existing behavior but prepare
next patch to make review easy.

Note: io_madvise pass NULL as target_task argument of do_madvise
because it couldn't know who is target.

[1] http://lore.kernel.org/r/CAG48ez27=pwm5m_N_988xT1huO7g7h6arTQL44zev6TD-h-7Tg@xxxxxxxxxxxxxx

Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
fs/io_uring.c | 2 +-
include/linux/mm.h | 3 ++-
mm/madvise.c | 34 +++++++++++++++++++---------------
3 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 63beda9bafc5..a858da2ae2f4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2736,7 +2736,7 @@ static int io_madvise(struct io_kiocb *req, struct io_kiocb **nxt,
if (force_nonblock)
return -EAGAIN;

- ret = do_madvise(ma->addr, ma->len, ma->advice);
+ ret = do_madvise(NULL, req->work.mm, ma->addr, ma->len, ma->advice);
if (ret < 0)
req_set_fail_links(req);
io_cqring_add_event(req, ret);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 52269e56c514..bc16c8774328 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2323,7 +2323,8 @@ extern int __do_munmap(struct mm_struct *, unsigned long, size_t,
struct list_head *uf, bool downgrade);
extern int do_munmap(struct mm_struct *, unsigned long, size_t,
struct list_head *uf);
-extern int do_madvise(unsigned long start, size_t len_in, int behavior);
+extern int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
+ unsigned long start, size_t len_in, int behavior);

static inline unsigned long
do_mmap_pgoff(struct file *file, unsigned long addr,
diff --git a/mm/madvise.c b/mm/madvise.c
index 43b47d3fae02..f75c86b6c463 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -254,6 +254,7 @@ static long madvise_willneed(struct vm_area_struct *vma,
struct vm_area_struct **prev,
unsigned long start, unsigned long end)
{
+ struct mm_struct *mm = vma->vm_mm;
struct file *file = vma->vm_file;
loff_t offset;

@@ -288,12 +289,12 @@ static long madvise_willneed(struct vm_area_struct *vma,
*/
*prev = NULL; /* tell sys_madvise we drop mmap_sem */
get_file(file);
- up_read(&current->mm->mmap_sem);
+ up_read(&mm->mmap_sem);
offset = (loff_t)(start - vma->vm_start)
+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
fput(file);
- down_read(&current->mm->mmap_sem);
+ down_read(&mm->mmap_sem);
return 0;
}

@@ -676,7 +677,6 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
if (nr_swap) {
if (current->mm == mm)
sync_mm_rss(mm);
-
add_mm_counter(mm, MM_SWAPENTS, nr_swap);
}
arch_leave_lazy_mmu_mode();
@@ -756,6 +756,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
unsigned long start, unsigned long end,
int behavior)
{
+ struct mm_struct *mm = vma->vm_mm;
+
*prev = vma;
if (!can_madv_lru_vma(vma))
return -EINVAL;
@@ -763,8 +765,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
if (!userfaultfd_remove(vma, start, end)) {
*prev = NULL; /* mmap_sem has been dropped, prev is stale */

- down_read(&current->mm->mmap_sem);
- vma = find_vma(current->mm, start);
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, start);
if (!vma)
return -ENOMEM;
if (start < vma->vm_start) {
@@ -818,6 +820,7 @@ static long madvise_remove(struct vm_area_struct *vma,
loff_t offset;
int error;
struct file *f;
+ struct mm_struct *mm = vma->vm_mm;

*prev = NULL; /* tell sys_madvise we drop mmap_sem */

@@ -845,13 +848,13 @@ static long madvise_remove(struct vm_area_struct *vma,
get_file(f);
if (userfaultfd_remove(vma, start, end)) {
/* mmap_sem was not released by userfaultfd_remove() */
- up_read(&current->mm->mmap_sem);
+ up_read(&mm->mmap_sem);
}
error = vfs_fallocate(f,
FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
offset, end - start);
fput(f);
- down_read(&current->mm->mmap_sem);
+ down_read(&mm->mmap_sem);
return error;
}

@@ -1044,7 +1047,8 @@ madvise_behavior_valid(int behavior)
* -EBADF - map exists, but area maps something that isn't a file.
* -EAGAIN - a kernel resource was temporarily unavailable.
*/
-int do_madvise(unsigned long start, size_t len_in, int behavior)
+int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
+ unsigned long start, size_t len_in, int behavior)
{
unsigned long end, tmp;
struct vm_area_struct *vma, *prev;
@@ -1082,10 +1086,10 @@ int do_madvise(unsigned long start, size_t len_in, int behavior)

write = madvise_need_mmap_write(behavior);
if (write) {
- if (down_write_killable(&current->mm->mmap_sem))
+ if (down_write_killable(&mm->mmap_sem))
return -EINTR;
} else {
- down_read(&current->mm->mmap_sem);
+ down_read(&mm->mmap_sem);
}

/*
@@ -1093,7 +1097,7 @@ int do_madvise(unsigned long start, size_t len_in, int behavior)
* ranges, just ignore them, but return -ENOMEM at the end.
* - different from the way of handling in mlock etc.
*/
- vma = find_vma_prev(current->mm, start, &prev);
+ vma = find_vma_prev(mm, start, &prev);
if (vma && start > vma->vm_start)
prev = vma;

@@ -1130,19 +1134,19 @@ int do_madvise(unsigned long start, size_t len_in, int behavior)
if (prev)
vma = prev->vm_next;
else /* madvise_remove dropped mmap_sem */
- vma = find_vma(current->mm, start);
+ vma = find_vma(mm, start);
}
out:
blk_finish_plug(&plug);
if (write)
- up_write(&current->mm->mmap_sem);
+ up_write(&mm->mmap_sem);
else
- up_read(&current->mm->mmap_sem);
+ up_read(&mm->mmap_sem);

return error;
}

SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
{
- return do_madvise(start, len_in, behavior);
+ return do_madvise(current, current->mm, start, len_in, behavior);
}
--
2.25.0.265.gbab2e86ba0-goog