* [PATCH v8 1/6] mm/vmalloc: extract vm_area_free_pages() helper from vfree()
2026-03-27 9:48 [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
@ 2026-03-27 9:48 ` Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 2/6] mm/vmalloc: fix vrealloc() grow-in-place check Shivam Kalra via B4 Relay
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6 siblings, 0 replies; 9+ messages in thread
From: Shivam Kalra via B4 Relay @ 2026-03-27 9:48 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki
Cc: linux-mm, linux-kernel, Alice Ryhl, Danilo Krummrich,
Shivam Kalra
From: Shivam Kalra <shivamkalra98@zohomail.in>
Extract the page-freeing loop and NR_VMALLOC stat accounting from
vfree() into a reusable vm_area_free_pages() helper. The helper operates
on a range [start_idx, end_idx) of pages from a vm_struct, making it
suitable for both full free (vfree) and partial free (upcoming vrealloc
shrink).
Freed page pointers in vm->pages[] are set to NULL to prevent stale
references when the vm_struct outlives the free (as in vrealloc shrink).
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
mm/vmalloc.c | 47 +++++++++++++++++++++++++++++++++--------------
1 file changed, 33 insertions(+), 14 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d75151649c97..79a57955345d 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3416,6 +3416,38 @@ void vfree_atomic(const void *addr)
schedule_work(&p->wq);
}
+/*
+ * vm_area_free_pages - free a range of pages from a vmalloc allocation
+ * @vm: the vm_struct containing the pages
+ * @start_idx: first page index to free (inclusive)
+ * @end_idx: last page index to free (exclusive)
+ *
+ * Free pages [start_idx, end_idx) updating NR_VMALLOC stat accounting.
+ * Freed vm->pages[] entries are set to NULL.
+ * Caller is responsible for unmapping (vunmap_range) and KASAN
+ * poisoning before calling this.
+ */
+static void vm_area_free_pages(struct vm_struct *vm, unsigned int start_idx,
+ unsigned int end_idx)
+{
+ unsigned int i;
+
+ for (i = start_idx; i < end_idx; i++) {
+ struct page *page = vm->pages[i];
+
+ BUG_ON(!page);
+ /*
+ * High-order allocs for huge vmallocs are split, so
+ * can be freed as an array of order-0 allocations
+ */
+ if (!(vm->flags & VM_MAP_PUT_PAGES))
+ mod_lruvec_page_state(page, NR_VMALLOC, -1);
+ __free_page(page);
+ vm->pages[i] = NULL;
+ cond_resched();
+ }
+}
+
/**
* vfree - Release memory allocated by vmalloc()
* @addr: Memory base address
@@ -3436,7 +3468,6 @@ void vfree_atomic(const void *addr)
void vfree(const void *addr)
{
struct vm_struct *vm;
- int i;
if (unlikely(in_interrupt())) {
vfree_atomic(addr);
@@ -3459,19 +3490,7 @@ void vfree(const void *addr)
if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
vm_reset_perms(vm);
- for (i = 0; i < vm->nr_pages; i++) {
- struct page *page = vm->pages[i];
-
- BUG_ON(!page);
- /*
- * High-order allocs for huge vmallocs are split, so
- * can be freed as an array of order-0 allocations
- */
- if (!(vm->flags & VM_MAP_PUT_PAGES))
- mod_lruvec_page_state(page, NR_VMALLOC, -1);
- __free_page(page);
- cond_resched();
- }
+ vm_area_free_pages(vm, 0, vm->nr_pages);
kvfree(vm->pages);
kfree(vm);
}
--
2.43.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH v8 2/6] mm/vmalloc: fix vrealloc() grow-in-place check
2026-03-27 9:48 [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 1/6] mm/vmalloc: extract vm_area_free_pages() helper from vfree() Shivam Kalra via B4 Relay
@ 2026-03-27 9:48 ` Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 3/6] mm/vmalloc: zero newly exposed memory on vrealloc() grow Shivam Kalra via B4 Relay
` (4 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: Shivam Kalra via B4 Relay @ 2026-03-27 9:48 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki
Cc: linux-mm, linux-kernel, Alice Ryhl, Danilo Krummrich,
Shivam Kalra
From: Shivam Kalra <shivamkalra98@zohomail.in>
Fix the grow-in-place check in vrealloc() to compare the requested size
against the actual physical page count (vm->nr_pages) rather than the
virtual area size (alloced_size, derived from get_vm_area_size()).
The virtual reservation size (get_vm_area_size()) does not decrease when
pages are freed during a shrink operation. Consequently, without this fix,
a subsequent grow-in-place operation after a shrink would incorrectly
succeed and attempt to access freed pages. Correcting this check is a
prerequisite for the upcoming vrealloc() shrink functionality.
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
mm/vmalloc.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 79a57955345d..133c3b0418fe 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4343,6 +4343,12 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align
if (unlikely(flags & __GFP_THISNODE) && nid != NUMA_NO_NODE &&
nid != page_to_nid(vmalloc_to_page(p)))
goto need_realloc;
+ } else {
+ /*
+ * If p is NULL, vrealloc behaves exactly like vmalloc.
+ * Skip the shrink and in-place grow paths.
+ */
+ goto need_realloc;
}
/*
@@ -4361,7 +4367,7 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align
/*
* We already have the bytes available in the allocation; use them.
*/
- if (size <= alloced_size) {
+ if (size <= (size_t)vm->nr_pages << PAGE_SHIFT) {
/*
* No need to zero memory here, as unused memory will have
* already been zeroed at initial allocation time or during
--
2.43.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH v8 3/6] mm/vmalloc: zero newly exposed memory on vrealloc() grow
2026-03-27 9:48 [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 1/6] mm/vmalloc: extract vm_area_free_pages() helper from vfree() Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 2/6] mm/vmalloc: fix vrealloc() grow-in-place check Shivam Kalra via B4 Relay
@ 2026-03-27 9:48 ` Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 4/6] mm/vmalloc: use READ_ONCE() for vmalloc nr_pages status readers Shivam Kalra via B4 Relay
` (3 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: Shivam Kalra via B4 Relay @ 2026-03-27 9:48 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki
Cc: linux-mm, linux-kernel, Alice Ryhl, Danilo Krummrich,
Shivam Kalra
From: Shivam Kalra <shivamkalra98@zohomail.in>
When growing an existing vmalloc allocation in-place, zero the newly
exposed memory region [old_size, size) if the caller requested it via
__GFP_ZERO (checked via want_init_on_alloc(flags)).
Previously, the code assumed that the unused capacity in the vm_struct
was already zeroed either at initial allocation time or during a prior
shrink. However, if an intermediate shrink operation occurred without
__GFP_ZERO and without init_on_free enabled, the "freed" portion of the
allocation would retain its old data.
If a subsequent grow-in-place operation then explicitly requests
__GFP_ZERO, failing to zero the memory here would violate the allocation
flags and leak the previously discarded, potentially sensitive data.
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
mm/vmalloc.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 133c3b0418fe..ddb689bf9ba5 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4368,13 +4368,16 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align
* We already have the bytes available in the allocation; use them.
*/
if (size <= (size_t)vm->nr_pages << PAGE_SHIFT) {
- /*
- * No need to zero memory here, as unused memory will have
- * already been zeroed at initial allocation time or during
- * realloc shrink time.
- */
vm->requested_size = size;
kasan_vrealloc(p, old_size, size);
+
+ /*
+ * Zero the newly exposed bytes if requested.
+ * The region [old_size, size) may contain stale data from
+ * a previous shrink that did not use __GFP_ZERO.
+ */
+ if (want_init_on_alloc(flags))
+ memset((void *)p + old_size, 0, size - old_size);
return (void *)p;
}
--
2.43.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH v8 4/6] mm/vmalloc: use READ_ONCE() for vmalloc nr_pages status readers
2026-03-27 9:48 [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
` (2 preceding siblings ...)
2026-03-27 9:48 ` [PATCH v8 3/6] mm/vmalloc: zero newly exposed memory on vrealloc() grow Shivam Kalra via B4 Relay
@ 2026-03-27 9:48 ` Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 5/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
` (2 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: Shivam Kalra via B4 Relay @ 2026-03-27 9:48 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki
Cc: linux-mm, linux-kernel, Alice Ryhl, Danilo Krummrich,
Shivam Kalra
From: Shivam Kalra <shivamkalra98@zohomail.in>
The vmalloc status readers (vmalloc_info_show(), show_numa_info(), and
vmalloc_dump_obj()) currently read v->nr_pages and the v->pages array
without any concurrent protection.
In preparation for vrealloc() shrink support, where v->nr_pages can
be decreased and entries in the v->pages array can be nulled out
concurrently, these readers must be protected to prevent use-after-free
or NULL pointer dereferences.
Update these functions to use READ_ONCE() when accessing v->nr_pages
and v->pages[nr]. This ensures the compiler does not re-fetch these
values and provides a consistent view of the vmap area's state.
Additionally, in show_numa_info(), explicitly check for a NULL page
pointer before dereferencing it to avoid potential crashes if a page
was concurrently removed during a shrink operation.
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
mm/vmalloc.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ddb689bf9ba5..c6bdddee6266 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -5189,7 +5189,7 @@ bool vmalloc_dump_obj(void *object)
vm = va->vm;
addr = (unsigned long) vm->addr;
caller = vm->caller;
- nr_pages = vm->nr_pages;
+ nr_pages = READ_ONCE(vm->nr_pages);
spin_unlock(&vn->busy.lock);
pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",
@@ -5210,7 +5210,7 @@ bool vmalloc_dump_obj(void *object)
static void show_numa_info(struct seq_file *m, struct vm_struct *v,
unsigned int *counters)
{
- unsigned int nr;
+ unsigned int nr, nr_pages;
unsigned int step = 1U << vm_area_page_order(v);
if (!counters)
@@ -5218,8 +5218,13 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v,
memset(counters, 0, nr_node_ids * sizeof(unsigned int));
- for (nr = 0; nr < v->nr_pages; nr += step)
- counters[page_to_nid(v->pages[nr])] += step;
+ nr_pages = READ_ONCE(v->nr_pages);
+ for (nr = 0; nr < nr_pages; nr += step) {
+ struct page *page = READ_ONCE(v->pages[nr]);
+
+ if (page)
+ counters[page_to_nid(page)] += step;
+ }
for_each_node_state(nr, N_HIGH_MEMORY)
if (counters[nr])
seq_printf(m, " N%u=%u", nr, counters[nr]);
@@ -5247,6 +5252,7 @@ static int vmalloc_info_show(struct seq_file *m, void *p)
struct vmap_area *va;
struct vm_struct *v;
unsigned int *counters;
+ unsigned int nr_pages;
if (IS_ENABLED(CONFIG_NUMA))
counters = kmalloc_array(nr_node_ids, sizeof(unsigned int), GFP_KERNEL);
@@ -5276,8 +5282,9 @@ static int vmalloc_info_show(struct seq_file *m, void *p)
if (v->caller)
seq_printf(m, " %pS", v->caller);
- if (v->nr_pages)
- seq_printf(m, " pages=%d", v->nr_pages);
+ nr_pages = READ_ONCE(v->nr_pages);
+ if (nr_pages)
+ seq_printf(m, " pages=%d", nr_pages);
if (v->phys_addr)
seq_printf(m, " phys=%pa", &v->phys_addr);
--
2.43.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH v8 5/6] mm/vmalloc: free unused pages on vrealloc() shrink
2026-03-27 9:48 [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
` (3 preceding siblings ...)
2026-03-27 9:48 ` [PATCH v8 4/6] mm/vmalloc: use READ_ONCE() for vmalloc nr_pages status readers Shivam Kalra via B4 Relay
@ 2026-03-27 9:48 ` Shivam Kalra via B4 Relay
2026-03-27 9:48 ` [PATCH v8 6/6] lib/test_vmalloc: add vrealloc test case Shivam Kalra via B4 Relay
2026-03-27 18:37 ` [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Andrew Morton
6 siblings, 0 replies; 9+ messages in thread
From: Shivam Kalra via B4 Relay @ 2026-03-27 9:48 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki
Cc: linux-mm, linux-kernel, Alice Ryhl, Danilo Krummrich,
Shivam Kalra
From: Shivam Kalra <shivamkalra98@zohomail.in>
When vrealloc() shrinks an allocation and the new size crosses a page
boundary, unmap and free the tail pages that are no longer needed. This
reclaims physical memory that was previously wasted for the lifetime
of the allocation.
The heuristic is simple: always free when at least one full page becomes
unused. Huge page allocations (page_order > 0) are skipped, as partial
freeing would require splitting. Allocations with VM_FLUSH_RESET_PERMS
are also skipped, as their direct-map permissions must be reset before
pages are returned to the page allocator, which is handled by
vm_reset_perms() during vfree().
Additionally, allocations with VM_USERMAP are skipped because
remap_vmalloc_range_partial() validates mapping requests against the
unchanged vm->size; freeing tail pages would cause vmalloc_to_page()
to return NULL for the unmapped range.
To protect concurrent readers, the shrink path uses Node lock to
synchronize before freeing the pages.
Finally, we notify kmemleak of the reduced allocation size using
kmemleak_free_part() to prevent the kmemleak scanner from faulting on
the newly unmapped virtual addresses.
The virtual address reservation (vm->size / vmap_area) is intentionally
kept unchanged, preserving the address for potential future grow-in-place
support.
Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
mm/vmalloc.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 52 insertions(+), 4 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index c6bdddee6266..57aec552e038 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4351,14 +4351,62 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align
goto need_realloc;
}
- /*
- * TODO: Shrink the vm_area, i.e. unmap and free unused pages. What
- * would be a good heuristic for when to shrink the vm_area?
- */
if (size <= old_size) {
+ unsigned int new_nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
/* Zero out "freed" memory, potentially for future realloc. */
if (want_init_on_free() || want_init_on_alloc(flags))
memset((void *)p + size, 0, old_size - size);
+
+ /*
+ * Free tail pages when shrink crosses a page boundary.
+ *
+ * Skip huge page allocations (page_order > 0) as partial
+ * freeing would require splitting.
+ *
+ * Skip VM_FLUSH_RESET_PERMS, as direct-map permissions must
+ * be reset before pages are returned to the allocator.
+ *
+ * Skip VM_USERMAP, as remap_vmalloc_range_partial() validates
+ * mapping requests against the unchanged vm->size; freeing
+ * tail pages would cause vmalloc_to_page() to return NULL for
+ * the unmapped range.
+ *
+ * Skip if either GFP_NOFS or GFP_NOIO are used.
+ * kmemleak_free_part() internally allocates with
+ * GFP_KERNEL, which could trigger a recursive deadlock
+ * if we are under filesystem or I/O reclaim.
+ */
+ if (new_nr_pages < vm->nr_pages && !vm_area_page_order(vm) &&
+ !(vm->flags & (VM_FLUSH_RESET_PERMS | VM_USERMAP)) &&
+ gfp_has_io_fs(flags)) {
+ unsigned long addr = (unsigned long)kasan_reset_tag(p);
+ unsigned int old_nr_pages = vm->nr_pages;
+
+ /* Notify kmemleak of the reduced allocation size before unmapping. */
+ kmemleak_free_part(
+ (void *)addr + ((unsigned long)new_nr_pages
+ << PAGE_SHIFT),
+ (unsigned long)(old_nr_pages - new_nr_pages)
+ << PAGE_SHIFT);
+
+ vunmap_range(addr + ((unsigned long)new_nr_pages
+ << PAGE_SHIFT),
+ addr + ((unsigned long)old_nr_pages
+ << PAGE_SHIFT));
+
+ /*
+ * Use the node lock to synchronize with concurrent
+ * readers (vmalloc_info_show).
+ */
+ struct vmap_node *vn = addr_to_node(addr);
+
+ spin_lock(&vn->busy.lock);
+ WRITE_ONCE(vm->nr_pages, new_nr_pages);
+ spin_unlock(&vn->busy.lock);
+
+ vm_area_free_pages(vm, new_nr_pages, old_nr_pages);
+ }
vm->requested_size = size;
kasan_vrealloc(p, old_size, size);
return (void *)p;
--
2.43.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH v8 6/6] lib/test_vmalloc: add vrealloc test case
2026-03-27 9:48 [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
` (4 preceding siblings ...)
2026-03-27 9:48 ` [PATCH v8 5/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
@ 2026-03-27 9:48 ` Shivam Kalra via B4 Relay
2026-03-27 18:37 ` [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Andrew Morton
6 siblings, 0 replies; 9+ messages in thread
From: Shivam Kalra via B4 Relay @ 2026-03-27 9:48 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki
Cc: linux-mm, linux-kernel, Alice Ryhl, Danilo Krummrich,
Shivam Kalra
From: Shivam Kalra <shivamkalra98@zohomail.in>
Introduce a new test case "vrealloc_test" that exercises the vrealloc()
shrink and in-place grow paths:
- Grow beyond allocated pages (triggers full reallocation).
- Shrink crossing a page boundary (frees tail pages).
- Shrink within the same page (no page freeing).
- Grow within the already allocated page count (in-place).
Data integrity is validated after each realloc step by checking that
the first byte of the original allocation is preserved.
The test is gated behind run_test_mask bit 12 (id 4096).
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
lib/test_vmalloc.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 62 insertions(+)
diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c
index 876c72c18a0c..b23f85e8f8ca 100644
--- a/lib/test_vmalloc.c
+++ b/lib/test_vmalloc.c
@@ -55,6 +55,7 @@ __param(int, run_test_mask, 7,
"\t\tid: 512, name: kvfree_rcu_2_arg_vmalloc_test\n"
"\t\tid: 1024, name: vm_map_ram_test\n"
"\t\tid: 2048, name: no_block_alloc_test\n"
+ "\t\tid: 4096, name: vrealloc_test\n"
/* Add a new test case description here. */
);
@@ -421,6 +422,66 @@ vm_map_ram_test(void)
return nr_allocated != map_nr_pages;
}
+static int vrealloc_test(void)
+{
+ void *ptr, *tmp;
+ int i;
+
+ for (i = 0; i < test_loop_count; i++) {
+ int err = -1;
+
+ ptr = vrealloc(NULL, PAGE_SIZE, GFP_KERNEL);
+ if (!ptr)
+ return -1;
+
+ *((__u8 *)ptr) = 'a';
+
+ /* Grow: beyond allocated pages, triggers full realloc. */
+ tmp = vrealloc(ptr, 4 * PAGE_SIZE, GFP_KERNEL);
+ if (!tmp)
+ goto error;
+ ptr = tmp;
+
+ if (*((__u8 *)ptr) != 'a')
+ goto error;
+
+ /* Shrink: crosses page boundary, frees tail pages. */
+ tmp = vrealloc(ptr, PAGE_SIZE, GFP_KERNEL);
+ if (!tmp)
+ goto error;
+ ptr = tmp;
+
+ if (*((__u8 *)ptr) != 'a')
+ goto error;
+
+ /* Shrink: within same page, no page freeing. */
+ tmp = vrealloc(ptr, PAGE_SIZE / 2, GFP_KERNEL);
+ if (!tmp)
+ goto error;
+ ptr = tmp;
+
+ if (*((__u8 *)ptr) != 'a')
+ goto error;
+
+ /* Grow: within allocated page, in-place, no realloc. */
+ tmp = vrealloc(ptr, PAGE_SIZE, GFP_KERNEL);
+ if (!tmp)
+ goto error;
+ ptr = tmp;
+
+ if (*((__u8 *)ptr) != 'a')
+ goto error;
+
+ err = 0;
+error:
+ vfree(ptr);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
struct test_case_desc {
const char *test_name;
int (*test_func)(void);
@@ -440,6 +501,7 @@ static struct test_case_desc test_case_array[] = {
{ "kvfree_rcu_2_arg_vmalloc_test", kvfree_rcu_2_arg_vmalloc_test, },
{ "vm_map_ram_test", vm_map_ram_test, },
{ "no_block_alloc_test", no_block_alloc_test, true },
+ { "vrealloc_test", vrealloc_test, },
/* Add a new test case here. */
};
--
2.43.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink
2026-03-27 9:48 [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Shivam Kalra via B4 Relay
` (5 preceding siblings ...)
2026-03-27 9:48 ` [PATCH v8 6/6] lib/test_vmalloc: add vrealloc test case Shivam Kalra via B4 Relay
@ 2026-03-27 18:37 ` Andrew Morton
2026-03-27 19:31 ` Danilo Krummrich
6 siblings, 1 reply; 9+ messages in thread
From: Andrew Morton @ 2026-03-27 18:37 UTC (permalink / raw)
To: shivamkalra98
Cc: Shivam Kalra via B4 Relay, Uladzislau Rezki, linux-mm,
linux-kernel, Alice Ryhl, Danilo Krummrich
On Fri, 27 Mar 2026 15:18:36 +0530 Shivam Kalra via B4 Relay <devnull+shivamkalra98.zohomail.in@kernel.org> wrote:
> This series implements the TODO in vrealloc() to unmap and free unused
> pages when shrinking across a page boundary.
Thanks. I'd prefer to defer this until the next -rc cycle
(https://lkml.kernel.org/r/20260323202941.08ddf2b0411501cae801ab4c@linux-foundation.org).
If Ulad would prefer that we push ahead then OK.
Are we able to describe how much memory this change might save under
various scenarios? If the savings are impressively large then that
would get attention.
AI review might have found a couple of things, one pre-existing:
https://sashiko.dev/#/patchset/20260327-vmalloc-shrink-v8-0-cc6b57059ed7@zohomail.in
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink
2026-03-27 18:37 ` [PATCH v8 0/6] mm/vmalloc: free unused pages on vrealloc() shrink Andrew Morton
@ 2026-03-27 19:31 ` Danilo Krummrich
0 siblings, 0 replies; 9+ messages in thread
From: Danilo Krummrich @ 2026-03-27 19:31 UTC (permalink / raw)
To: Andrew Morton
Cc: shivamkalra98, Shivam Kalra via B4 Relay, Uladzislau Rezki,
linux-mm, linux-kernel, Alice Ryhl
On Fri Mar 27, 2026 at 7:37 PM CET, Andrew Morton wrote:
> Are we able to describe how much memory this change might save under
> various scenarios? If the savings are impressively large then that
> would get attention.
We already have a workaround in place for shrinking vmalloc buffers through a
deep copy in Rust alloc.
Given that binder, which motivated this workaround, uses it already, it suggests
that the savings are significant enough to accept this overhead (I assume Alice
has some numbers).
So, I assume the more interesting question would be how badly the deep copy
hurts binder compared to unmapping and freeing spare pages.
^ permalink raw reply [flat|nested] 9+ messages in thread