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Subject[RFC 4/7] mm: factor out madvise's core functionality
Date
This patch factor out madvise's core functionality so that upcoming
patch can reuse it without duplication.

It shouldn't change any behavior.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
mm/madvise.c | 168 +++++++++++++++++++++++++++------------------------
1 file changed, 89 insertions(+), 79 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 9a6698b56845..119e82e1f065 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -742,7 +742,8 @@ static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
return 0;
}

-static long madvise_dontneed_free(struct vm_area_struct *vma,
+static long madvise_dontneed_free(struct task_struct *tsk,
+ struct vm_area_struct *vma,
struct vm_area_struct **prev,
unsigned long start, unsigned long end,
int behavior)
@@ -754,8 +755,8 @@ 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(&tsk->mm->mmap_sem);
+ vma = find_vma(tsk->mm, start);
if (!vma)
return -ENOMEM;
if (start < vma->vm_start) {
@@ -802,7 +803,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
* Application wants to free up the pages and associated backing store.
* This is effectively punching a hole into the middle of a file.
*/
-static long madvise_remove(struct vm_area_struct *vma,
+static long madvise_remove(struct task_struct *tsk,
+ struct vm_area_struct *vma,
struct vm_area_struct **prev,
unsigned long start, unsigned long end)
{
@@ -836,13 +838,13 @@ 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(&tsk->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(&tsk->mm->mmap_sem);
return error;
}

@@ -916,12 +918,13 @@ static int madvise_inject_error(int behavior,
#endif

static long
-madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
- unsigned long start, unsigned long end, int behavior)
+madvise_vma(struct task_struct *tsk, struct vm_area_struct *vma,
+ struct vm_area_struct **prev, unsigned long start,
+ unsigned long end, int behavior)
{
switch (behavior) {
case MADV_REMOVE:
- return madvise_remove(vma, prev, start, end);
+ return madvise_remove(tsk, vma, prev, start, end);
case MADV_WILLNEED:
return madvise_willneed(vma, prev, start, end);
case MADV_COOL:
@@ -930,7 +933,8 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
return madvise_cold(vma, start, end);
case MADV_FREE:
case MADV_DONTNEED:
- return madvise_dontneed_free(vma, prev, start, end, behavior);
+ return madvise_dontneed_free(tsk, vma, prev, start,
+ end, behavior);
default:
return madvise_behavior(vma, prev, start, end, behavior);
}
@@ -974,68 +978,8 @@ madvise_behavior_valid(int behavior)
}
}

-/*
- * The madvise(2) system call.
- *
- * Applications can use madvise() to advise the kernel how it should
- * handle paging I/O in this VM area. The idea is to help the kernel
- * use appropriate read-ahead and caching techniques. The information
- * provided is advisory only, and can be safely disregarded by the
- * kernel without affecting the correct operation of the application.
- *
- * behavior values:
- * MADV_NORMAL - the default behavior is to read clusters. This
- * results in some read-ahead and read-behind.
- * MADV_RANDOM - the system should read the minimum amount of data
- * on any access, since it is unlikely that the appli-
- * cation will need more than what it asks for.
- * MADV_SEQUENTIAL - pages in the given range will probably be accessed
- * once, so they can be aggressively read ahead, and
- * can be freed soon after they are accessed.
- * MADV_WILLNEED - the application is notifying the system to read
- * some pages ahead.
- * MADV_DONTNEED - the application is finished with the given range,
- * so the kernel can free resources associated with it.
- * MADV_FREE - the application marks pages in the given range as lazy free,
- * where actual purges are postponed until memory pressure happens.
- * MADV_REMOVE - the application wants to free up the given range of
- * pages and associated backing store.
- * MADV_DONTFORK - omit this area from child's address space when forking:
- * typically, to avoid COWing pages pinned by get_user_pages().
- * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
- * MADV_WIPEONFORK - present the child process with zero-filled memory in this
- * range after a fork.
- * MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
- * MADV_HWPOISON - trigger memory error handler as if the given memory range
- * were corrupted by unrecoverable hardware memory failure.
- * MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
- * MADV_MERGEABLE - the application recommends that KSM try to merge pages in
- * this area with pages of identical content from other such areas.
- * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
- * MADV_HUGEPAGE - the application wants to back the given range by transparent
- * huge pages in the future. Existing pages might be coalesced and
- * new pages might be allocated as THP.
- * MADV_NOHUGEPAGE - mark the given range as not worth being backed by
- * transparent huge pages so the existing pages will not be
- * coalesced into THP and new pages will not be allocated as THP.
- * MADV_DONTDUMP - the application wants to prevent pages in the given range
- * from being included in its core dump.
- * MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
- *
- * return values:
- * zero - success
- * -EINVAL - start + len < 0, start is not page-aligned,
- * "behavior" is not a valid value, or application
- * is attempting to release locked or shared pages,
- * or the specified address range includes file, Huge TLB,
- * MAP_SHARED or VMPFNMAP range.
- * -ENOMEM - addresses in the specified range are not currently
- * mapped, or are outside the AS of the process.
- * -EIO - an I/O error occurred while paging in data.
- * -EBADF - map exists, but area maps something that isn't a file.
- * -EAGAIN - a kernel resource was temporarily unavailable.
- */
-SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
+static int madvise_core(struct task_struct *tsk, unsigned long start,
+ size_t len_in, int behavior)
{
unsigned long end, tmp;
struct vm_area_struct *vma, *prev;
@@ -1071,10 +1015,10 @@ SYSCALL_DEFINE3(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(&tsk->mm->mmap_sem))
return -EINTR;
} else {
- down_read(&current->mm->mmap_sem);
+ down_read(&tsk->mm->mmap_sem);
}

/*
@@ -1082,7 +1026,7 @@ SYSCALL_DEFINE3(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(tsk->mm, start, &prev);
if (vma && start > vma->vm_start)
prev = vma;

@@ -1107,7 +1051,7 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
tmp = end;

/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
- error = madvise_vma(vma, &prev, start, tmp, behavior);
+ error = madvise_vma(tsk, vma, &prev, start, tmp, behavior);
if (error)
goto out;
start = tmp;
@@ -1119,14 +1063,80 @@ SYSCALL_DEFINE3(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(tsk->mm, start);
}
out:
blk_finish_plug(&plug);
if (write)
- up_write(&current->mm->mmap_sem);
+ up_write(&tsk->mm->mmap_sem);
else
- up_read(&current->mm->mmap_sem);
+ up_read(&tsk->mm->mmap_sem);

return error;
}
+
+/*
+ * The madvise(2) system call.
+ *
+ * Applications can use madvise() to advise the kernel how it should
+ * handle paging I/O in this VM area. The idea is to help the kernel
+ * use appropriate read-ahead and caching techniques. The information
+ * provided is advisory only, and can be safely disregarded by the
+ * kernel without affecting the correct operation of the application.
+ *
+ * behavior values:
+ * MADV_NORMAL - the default behavior is to read clusters. This
+ * results in some read-ahead and read-behind.
+ * MADV_RANDOM - the system should read the minimum amount of data
+ * on any access, since it is unlikely that the appli-
+ * cation will need more than what it asks for.
+ * MADV_SEQUENTIAL - pages in the given range will probably be accessed
+ * once, so they can be aggressively read ahead, and
+ * can be freed soon after they are accessed.
+ * MADV_WILLNEED - the application is notifying the system to read
+ * some pages ahead.
+ * MADV_DONTNEED - the application is finished with the given range,
+ * so the kernel can free resources associated with it.
+ * MADV_FREE - the application marks pages in the given range as lazy free,
+ * where actual purges are postponed until memory pressure happens.
+ * MADV_REMOVE - the application wants to free up the given range of
+ * pages and associated backing store.
+ * MADV_DONTFORK - omit this area from child's address space when forking:
+ * typically, to avoid COWing pages pinned by get_user_pages().
+ * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
+ * MADV_WIPEONFORK - present the child process with zero-filled memory in this
+ * range after a fork.
+ * MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
+ * MADV_HWPOISON - trigger memory error handler as if the given memory range
+ * were corrupted by unrecoverable hardware memory failure.
+ * MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
+ * MADV_MERGEABLE - the application recommends that KSM try to merge pages in
+ * this area with pages of identical content from other such areas.
+ * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
+ * MADV_HUGEPAGE - the application wants to back the given range by transparent
+ * huge pages in the future. Existing pages might be coalesced and
+ * new pages might be allocated as THP.
+ * MADV_NOHUGEPAGE - mark the given range as not worth being backed by
+ * transparent huge pages so the existing pages will not be
+ * coalesced into THP and new pages will not be allocated as THP.
+ * MADV_DONTDUMP - the application wants to prevent pages in the given range
+ * from being included in its core dump.
+ * MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
+ *
+ * return values:
+ * zero - success
+ * -EINVAL - start + len < 0, start is not page-aligned,
+ * "behavior" is not a valid value, or application
+ * is attempting to release locked or shared pages,
+ * or the specified address range includes file, Huge TLB,
+ * MAP_SHARED or VMPFNMAP range.
+ * -ENOMEM - addresses in the specified range are not currently
+ * mapped, or are outside the AS of the process.
+ * -EIO - an I/O error occurred while paging in data.
+ * -EBADF - map exists, but area maps something that isn't a file.
+ * -EAGAIN - a kernel resource was temporarily unavailable.
+ */
+SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
+{
+ return madvise_core(current, start, len_in, behavior);
+}
--
2.21.0.1020.gf2820cf01a-goog
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