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Message-ID: <20240531163217.1584450-3-Liam.Howlett@oracle.com>
Date: Fri, 31 May 2024 12:32:14 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Suren Baghdasaryan <surenb@...gle.com>,
Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Vlastimil Babka <vbabka@...e.cz>, sidhartha.kumar@...cle.com,
Matthew Wilcox <willy@...radead.org>,
Lorenzo Stoakes <lstoakes@...il.com>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
linux-fsdevel@...r.kernel.org, bpf@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/5] mm/mmap: Split do_vmi_align_munmap() into a gather and complete operation
Split the munmap function into a gathering of vmas and a cleanup of the
gathered vmas. This is necessary for the later patches in the series.
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
mm/mmap.c | 143 ++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 101 insertions(+), 42 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 31d464e6a656..fad40d604c64 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2340,6 +2340,7 @@ static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas)
if (vma->vm_flags & VM_ACCOUNT)
nr_accounted += nrpages;
+
vm_stat_account(mm, vma->vm_flags, -nrpages);
remove_vma(vma, false);
}
@@ -2545,33 +2546,45 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
vma->vm_userfaultfd_ctx, anon_vma_name(vma));
}
+
+static inline void abort_munmap_vmas(struct ma_state *mas_detach)
+{
+ struct vm_area_struct *vma;
+ int limit;
+
+ limit = mas_detach->index;
+ mas_set(mas_detach, 0);
+ /* Re-attach any detached VMAs */
+ mas_for_each(mas_detach, vma, limit)
+ vma_mark_detached(vma, false);
+
+ __mt_destroy(mas_detach->tree);
+}
+
/*
- * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
+ * vmi_gather_munmap_vmas() - Put all VMAs within a range into a maple tree
+ * for removal at a later date. Handles splitting first and last if necessary
+ * and marking the vmas as isolated.
+ *
* @vmi: The vma iterator
* @vma: The starting vm_area_struct
* @mm: The mm_struct
* @start: The aligned start address to munmap.
* @end: The aligned end address to munmap.
* @uf: The userfaultfd list_head
- * @unlock: Set to true to drop the mmap_lock. unlocking only happens on
- * success.
+ * @mas_detach: The maple state tracking the detached tree
*
- * Return: 0 on success and drops the lock if so directed, error and leaves the
- * lock held otherwise.
+ * Return: 0 on success
*/
static int
-do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
+vmi_gather_munmap_vmas(struct vma_iterator *vmi, struct vm_area_struct *vma,
struct mm_struct *mm, unsigned long start,
- unsigned long end, struct list_head *uf, bool unlock)
+ unsigned long end, struct list_head *uf,
+ struct ma_state *mas_detach, unsigned long *locked_vm)
{
- struct vm_area_struct *prev, *next = NULL;
- struct maple_tree mt_detach;
- int count = 0;
+ struct vm_area_struct *next = NULL;
int error = -ENOMEM;
- unsigned long locked_vm = 0;
- MA_STATE(mas_detach, &mt_detach, 0, 0);
- mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
- mt_on_stack(mt_detach);
+ int count = 0;
/*
* If we need to split any vma, do it now to save pain later.
@@ -2610,15 +2623,14 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
goto end_split_failed;
}
vma_start_write(next);
- mas_set(&mas_detach, count);
- error = mas_store_gfp(&mas_detach, next, GFP_KERNEL);
+ mas_set(mas_detach, count++);
+ if (next->vm_flags & VM_LOCKED)
+ *locked_vm += vma_pages(next);
+
+ error = mas_store_gfp(mas_detach, next, GFP_KERNEL);
if (error)
goto munmap_gather_failed;
vma_mark_detached(next, true);
- if (next->vm_flags & VM_LOCKED)
- locked_vm += vma_pages(next);
-
- count++;
if (unlikely(uf)) {
/*
* If userfaultfd_unmap_prep returns an error the vmas
@@ -2643,7 +2655,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
/* Make sure no VMAs are about to be lost. */
{
- MA_STATE(test, &mt_detach, 0, 0);
+ MA_STATE(test, mas_detach->tree, 0, 0);
struct vm_area_struct *vma_mas, *vma_test;
int test_count = 0;
@@ -2663,13 +2675,29 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
while (vma_iter_addr(vmi) > start)
vma_iter_prev_range(vmi);
- error = vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL);
- if (error)
- goto clear_tree_failed;
+ return 0;
- /* Point of no return */
- mm->locked_vm -= locked_vm;
+userfaultfd_error:
+munmap_gather_failed:
+end_split_failed:
+ abort_munmap_vmas(mas_detach);
+start_split_failed:
+map_count_exceeded:
+ return error;
+}
+
+static void
+vmi_complete_munmap_vmas(struct vma_iterator *vmi, struct vm_area_struct *vma,
+ struct mm_struct *mm, unsigned long start,
+ unsigned long end, bool unlock, struct ma_state *mas_detach,
+ unsigned long locked_vm)
+{
+ struct vm_area_struct *prev, *next;
+ int count;
+
+ count = mas_detach->index + 1;
mm->map_count -= count;
+ mm->locked_vm -= locked_vm;
if (unlock)
mmap_write_downgrade(mm);
@@ -2682,30 +2710,61 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
* We can free page tables without write-locking mmap_lock because VMAs
* were isolated before we downgraded mmap_lock.
*/
- mas_set(&mas_detach, 1);
- unmap_region(mm, &mas_detach, vma, prev, next, start, end, count,
+ mas_set(mas_detach, 1);
+ unmap_region(mm, mas_detach, vma, prev, next, start, end, count,
!unlock);
/* Statistics and freeing VMAs */
- mas_set(&mas_detach, 0);
- remove_mt(mm, &mas_detach);
+ mas_set(mas_detach, 0);
+ remove_mt(mm, mas_detach);
validate_mm(mm);
if (unlock)
mmap_read_unlock(mm);
- __mt_destroy(&mt_detach);
- return 0;
+ __mt_destroy(mas_detach->tree);
+}
-clear_tree_failed:
-userfaultfd_error:
-munmap_gather_failed:
-end_split_failed:
- mas_set(&mas_detach, 0);
- mas_for_each(&mas_detach, next, end)
- vma_mark_detached(next, false);
+/*
+ * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
+ * @vmi: The vma iterator
+ * @vma: The starting vm_area_struct
+ * @mm: The mm_struct
+ * @start: The aligned start address to munmap.
+ * @end: The aligned end address to munmap.
+ * @uf: The userfaultfd list_head
+ * @unlock: Set to true to drop the mmap_lock. unlocking only happens on
+ * success.
+ *
+ * Return: 0 on success and drops the lock if so directed, error and leaves the
+ * lock held otherwise.
+ */
+static int
+do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
+ struct mm_struct *mm, unsigned long start,
+ unsigned long end, struct list_head *uf, bool unlock)
+{
+ struct maple_tree mt_detach;
+ MA_STATE(mas_detach, &mt_detach, 0, 0);
+ mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
+ mt_on_stack(mt_detach);
+ int error;
+ unsigned long locked_vm = 0;
- __mt_destroy(&mt_detach);
-start_split_failed:
-map_count_exceeded:
+ error = vmi_gather_munmap_vmas(vmi, vma, mm, start, end, uf,
+ &mas_detach, &locked_vm);
+ if (error)
+ goto gather_failed;
+
+ error = vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL);
+ if (error)
+ goto clear_area_failed;
+
+ vmi_complete_munmap_vmas(vmi, vma, mm, start, end, unlock, &mas_detach,
+ locked_vm);
+ return 0;
+
+clear_area_failed:
+ abort_munmap_vmas(&mas_detach);
+gather_failed:
validate_mm(mm);
return error;
}
--
2.43.0
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