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Message-ID: <4239e727b98763856b86cbd9eeaa0ba792eb2394.1750363557.git.lorenzo.stoakes@oracle.com>
Date: Thu, 19 Jun 2025 21:26:26 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>, Zi Yan <ziy@...dia.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Lance Yang <ioworker0@...il.com>, SeongJae Park <sj@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH 1/5] mm/madvise: remove the visitor pattern and thread anon_vma state
Now we have the madvise_behavior helper struct we no longer need to mess
around with void* pointers in order to propagate anon_vma_name, and this
means we can get rid of the confusing and inconsistent visitor pattern
implementation in madvise_vma_anon_name().
This means we now have a single state object that threads through most of
madvise()'s logic and a single code path which executes the majority of
madvise() behaviour (we maintain separate logic for failure injection and
memory population for the time being).
Note that users cannot inadvertently cause this behaviour to occur, as
madvise_behavior_valid() would reject it.
Doing this results in a can_modify_vma_madv() check for anonymous VMA name
changes, however this will cause no issues as this operation is not
prohibited.
We can also then reuse more code and drop the redundant
madvise_vma_anon_name() function altogether.
Additionally separate out behaviours that update VMAs from those that do
not.
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
mm/madvise.c | 167 +++++++++++++++++++++++++++------------------------
1 file changed, 90 insertions(+), 77 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index 070132f9842b..9dd935d64692 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -37,6 +37,9 @@
#include "internal.h"
#include "swap.h"
+#define __MADV_SET_ANON_VMA_NAME (-1)
+#define __MADV_CLEAR_ANON_VMA_NAME (-2)
+
/*
* Maximum number of attempts we make to install guard pages before we give up
* and return -ERESTARTNOINTR to have userspace try again.
@@ -59,9 +62,13 @@ struct madvise_behavior {
int behavior;
struct mmu_gather *tlb;
enum madvise_lock_mode lock_mode;
+ struct anon_vma_name *anon_name;
};
#ifdef CONFIG_ANON_VMA_NAME
+static int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
+ unsigned long end, struct madvise_behavior *madv_behavior);
+
struct anon_vma_name *anon_vma_name_alloc(const char *name)
{
struct anon_vma_name *anon_name;
@@ -112,6 +119,48 @@ static int replace_anon_vma_name(struct vm_area_struct *vma,
return 0;
}
+
+int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
+ unsigned long len_in, struct anon_vma_name *anon_name)
+{
+ unsigned long end;
+ unsigned long len;
+ struct madvise_behavior madv_behavior = {
+ .lock_mode = MADVISE_MMAP_WRITE_LOCK,
+ .anon_name = anon_name,
+ };
+
+ if (start & ~PAGE_MASK)
+ return -EINVAL;
+ len = (len_in + ~PAGE_MASK) & PAGE_MASK;
+
+ /* Check to see whether len was rounded up from small -ve to zero */
+ if (len_in && !len)
+ return -EINVAL;
+
+ end = start + len;
+ if (end < start)
+ return -EINVAL;
+
+ if (end == start)
+ return 0;
+
+ madv_behavior.behavior =
+ anon_name ? __MADV_SET_ANON_VMA_NAME : __MADV_CLEAR_ANON_VMA_NAME;
+
+ return madvise_walk_vmas(mm, start, end, &madv_behavior);
+}
+
+static bool is_anon_vma_name(int behavior)
+{
+ switch (behavior) {
+ case __MADV_SET_ANON_VMA_NAME:
+ case __MADV_CLEAR_ANON_VMA_NAME:
+ return true;
+ default:
+ return false;
+ }
+}
#else /* CONFIG_ANON_VMA_NAME */
static int replace_anon_vma_name(struct vm_area_struct *vma,
struct anon_vma_name *anon_name)
@@ -121,6 +170,11 @@ static int replace_anon_vma_name(struct vm_area_struct *vma,
return 0;
}
+
+static bool is_anon_vma_name(int behavior)
+{
+ return false;
+}
#endif /* CONFIG_ANON_VMA_NAME */
/*
* Update the vm_flags on region of a vma, splitting it or merging it as
@@ -1252,13 +1306,12 @@ static long madvise_guard_remove(struct vm_area_struct *vma,
static int madvise_vma_behavior(struct vm_area_struct *vma,
struct vm_area_struct **prev,
unsigned long start, unsigned long end,
- void *behavior_arg)
+ struct madvise_behavior *madv_behavior)
{
- struct madvise_behavior *arg = behavior_arg;
- int behavior = arg->behavior;
- int error;
- struct anon_vma_name *anon_name;
+ int behavior = madv_behavior->behavior;
+ struct anon_vma_name *anon_name = madv_behavior->anon_name;
vm_flags_t new_flags = vma->vm_flags;
+ int error;
if (unlikely(!can_modify_vma_madv(vma, behavior)))
return -EPERM;
@@ -1275,7 +1328,17 @@ static int madvise_vma_behavior(struct vm_area_struct *vma,
case MADV_FREE:
case MADV_DONTNEED:
case MADV_DONTNEED_LOCKED:
- return madvise_dontneed_free(vma, prev, start, end, arg);
+ return madvise_dontneed_free(vma, prev, start, end,
+ madv_behavior);
+ case MADV_COLLAPSE:
+ return madvise_collapse(vma, prev, start, end);
+ case MADV_GUARD_INSTALL:
+ return madvise_guard_install(vma, prev, start, end);
+ case MADV_GUARD_REMOVE:
+ return madvise_guard_remove(vma, prev, start, end);
+
+ /* The below behaviours update VMAs via madvise_update_vma(). */
+
case MADV_NORMAL:
new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
break;
@@ -1325,21 +1388,25 @@ static int madvise_vma_behavior(struct vm_area_struct *vma,
if (error)
goto out;
break;
- case MADV_COLLAPSE:
- return madvise_collapse(vma, prev, start, end);
- case MADV_GUARD_INSTALL:
- return madvise_guard_install(vma, prev, start, end);
- case MADV_GUARD_REMOVE:
- return madvise_guard_remove(vma, prev, start, end);
+ case __MADV_SET_ANON_VMA_NAME:
+ case __MADV_CLEAR_ANON_VMA_NAME:
+ /* Only anonymous mappings can be named */
+ if (vma->vm_file && !vma_is_anon_shmem(vma))
+ return -EBADF;
+ break;
}
/* We cannot provide prev in this lock mode. */
- VM_WARN_ON_ONCE(arg->lock_mode == MADVISE_VMA_READ_LOCK);
- anon_name = anon_vma_name(vma);
- anon_vma_name_get(anon_name);
+ VM_WARN_ON_ONCE(madv_behavior->lock_mode == MADVISE_VMA_READ_LOCK);
+
+ if (!is_anon_vma_name(behavior)) {
+ anon_name = anon_vma_name(vma);
+ anon_vma_name_get(anon_name);
+ }
error = madvise_update_vma(vma, prev, start, end, new_flags,
anon_name);
- anon_vma_name_put(anon_name);
+ if (!is_anon_vma_name(behavior))
+ anon_vma_name_put(anon_name);
out:
/*
@@ -1532,11 +1599,7 @@ static struct vm_area_struct *try_vma_read_lock(struct mm_struct *mm,
*/
static
int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
- unsigned long end, struct madvise_behavior *madv_behavior,
- void *arg,
- int (*visit)(struct vm_area_struct *vma,
- struct vm_area_struct **prev, unsigned long start,
- unsigned long end, void *arg))
+ unsigned long end, struct madvise_behavior *madv_behavior)
{
struct vm_area_struct *vma;
struct vm_area_struct *prev;
@@ -1548,11 +1611,12 @@ int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
* If VMA read lock is supported, apply madvise to a single VMA
* tentatively, avoiding walking VMAs.
*/
- if (madv_behavior && madv_behavior->lock_mode == MADVISE_VMA_READ_LOCK) {
+ if (madv_behavior->lock_mode == MADVISE_VMA_READ_LOCK) {
vma = try_vma_read_lock(mm, madv_behavior, start, end);
if (vma) {
prev = vma;
- error = visit(vma, &prev, start, end, arg);
+ error = madvise_vma_behavior(vma, &prev, start, end,
+ madv_behavior);
vma_end_read(vma);
return error;
}
@@ -1586,7 +1650,8 @@ int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
tmp = end;
/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
- error = visit(vma, &prev, start, tmp, arg);
+ error = madvise_vma_behavior(vma, &prev, start, tmp,
+ madv_behavior);
if (error)
return error;
start = tmp;
@@ -1603,57 +1668,6 @@ int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
return unmapped_error;
}
-#ifdef CONFIG_ANON_VMA_NAME
-static int madvise_vma_anon_name(struct vm_area_struct *vma,
- struct vm_area_struct **prev,
- unsigned long start, unsigned long end,
- void *anon_name)
-{
- int error;
-
- /* Only anonymous mappings can be named */
- if (vma->vm_file && !vma_is_anon_shmem(vma))
- return -EBADF;
-
- error = madvise_update_vma(vma, prev, start, end, vma->vm_flags,
- anon_name);
-
- /*
- * madvise() returns EAGAIN if kernel resources, such as
- * slab, are temporarily unavailable.
- */
- if (error == -ENOMEM)
- error = -EAGAIN;
- return error;
-}
-
-int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
- unsigned long len_in, struct anon_vma_name *anon_name)
-{
- unsigned long end;
- unsigned long len;
-
- if (start & ~PAGE_MASK)
- return -EINVAL;
- len = (len_in + ~PAGE_MASK) & PAGE_MASK;
-
- /* Check to see whether len was rounded up from small -ve to zero */
- if (len_in && !len)
- return -EINVAL;
-
- end = start + len;
- if (end < start)
- return -EINVAL;
-
- if (end == start)
- return 0;
-
- return madvise_walk_vmas(mm, start, end, NULL, anon_name,
- madvise_vma_anon_name);
-}
-#endif /* CONFIG_ANON_VMA_NAME */
-
-
/*
* Any behaviour which results in changes to the vma->vm_flags needs to
* take mmap_lock for writing. Others, which simply traverse vmas, need
@@ -1845,8 +1859,7 @@ static int madvise_do_behavior(struct mm_struct *mm,
if (is_madvise_populate(behavior))
error = madvise_populate(mm, start, end, behavior);
else
- error = madvise_walk_vmas(mm, start, end, madv_behavior,
- madv_behavior, madvise_vma_behavior);
+ error = madvise_walk_vmas(mm, start, end, madv_behavior);
blk_finish_plug(&plug);
return error;
}
--
2.49.0
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