The quilt patch titled
Subject: mm/vmalloc.c: add used_map into vmap_block to track space of vmap_block
has been removed from the -mm tree. Its filename was
mm-vmallocc-add-used_map-into-vmap_block-to-track-space-of-vmap_block.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
From: Baoquan He <bhe@xxxxxxxxxx>
Subject: mm/vmalloc.c: add used_map into vmap_block to track space of vmap_block
Date: Fri, 13 Jan 2023 11:19:15 +0800
Patch series "mm/vmalloc.c: allow vread() to read out vm_map_ram areas",
v3.
Problem:
***
Stephen reported vread() will skip vm_map_ram areas when reading out
/proc/kcore with drgn utility. Please see below link to get more
details.
/proc/kcore reads 0's for vmap_block
https://lore.kernel.org/all/87ilk6gos2.fsf@xxxxxxxxxx/T/#u
Root cause:
***
The normal vmalloc API uses struct vmap_area to manage the virtual
kernel area allocated, and associate a vm_struct to store more
information and pass out. However, area reserved through vm_map_ram()
interface doesn't allocate vm_struct to associate with. So the current
code in vread() will skip the vm_map_ram area through 'if (!va->vm)'
conditional checking.
Solution:
***
To mark the area reserved through vm_map_ram() interface, add field 'flags'
into struct vmap_area. Bit 0 indicates this is vm_map_ram area created
through vm_map_ram() interface, bit 1 marks out the type of vm_map_ram area
which makes use of vmap_block to manage split regions via vb_alloc/free().
And also add bitmap field 'used_map' into struct vmap_block to mark those
further subdivided regions being used to differentiate with dirty and free
regions in vmap_block.
With the help of above vmap_area->flags and vmap_block->used_map, we can
recognize and handle vm_map_ram areas successfully. All these are done
in patch 1~3.
Meanwhile, do some improvement on areas related to vm_map_ram areas in
patch 4, 5. And also change area flag from VM_ALLOC to VM_IOREMAP in
patch 6, 7 because this will show them as 'ioremap' in /proc/vmallocinfo,
and exclude them from /proc/kcore.
Testing
***
Only did the basic testing on kvm guest, and run below command to
access kcore file to do statistics:
makedumpfile --mem-usage /proc/kcore
This patch (of 7):
In one vmap_block area, there could be three types of regions: region
being used which is allocated through vb_alloc(), dirty region which is
freed via vb_free() and free region. Among them, only used region has
available data. While there's no way to track those used regions
currently.
Here, add bitmap field used_map into vmap_block, and set/clear it during
allocation or freeing regions of vmap_block area.
This is a preparation for later use.
Link: https://lkml.kernel.org/r/20230113031921.64716-1-bhe@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20230113031921.64716-2-bhe@xxxxxxxxxx
Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Reported-by: Stephen Brennan <stephen.s.brennan@xxxxxxxxxx>
Link: https://lore.kernel.org/all/87ilk6gos2.fsf@xxxxxxxxxx/T/#u
Reviewed-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/vmalloc.c~mm-vmallocc-add-used_map-into-vmap_block-to-track-space-of-vmap_block
+++ a/mm/vmalloc.c
@@ -1922,6 +1922,7 @@ struct vmap_block {
spinlock_t lock;
struct vmap_area *va;
unsigned long free, dirty;
+ DECLARE_BITMAP(used_map, VMAP_BBMAP_BITS);
unsigned long dirty_min, dirty_max; /*< dirty range */
struct list_head free_list;
struct rcu_head rcu_head;
@@ -1998,10 +1999,12 @@ static void *new_vmap_block(unsigned int
vb->va = va;
/* At least something should be left free */
BUG_ON(VMAP_BBMAP_BITS <= (1UL << order));
+ bitmap_zero(vb->used_map, VMAP_BBMAP_BITS);
vb->free = VMAP_BBMAP_BITS - (1UL << order);
vb->dirty = 0;
vb->dirty_min = VMAP_BBMAP_BITS;
vb->dirty_max = 0;
+ bitmap_set(vb->used_map, 0, (1UL << order));
INIT_LIST_HEAD(&vb->free_list);
vb_idx = addr_to_vb_idx(va->va_start);
@@ -2111,6 +2114,7 @@ static void *vb_alloc(unsigned long size
pages_off = VMAP_BBMAP_BITS - vb->free;
vaddr = vmap_block_vaddr(vb->va->va_start, pages_off);
vb->free -= 1UL << order;
+ bitmap_set(vb->used_map, pages_off, (1UL << order));
if (vb->free == 0) {
spin_lock(&vbq->lock);
list_del_rcu(&vb->free_list);
@@ -2144,6 +2148,9 @@ static void vb_free(unsigned long addr,
order = get_order(size);
offset = (addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;
vb = xa_load(&vmap_blocks, addr_to_vb_idx(addr));
+ spin_lock(&vb->lock);
+ bitmap_clear(vb->used_map, offset, (1UL << order));
+ spin_unlock(&vb->lock);
vunmap_range_noflush(addr, addr + size);
_
Patches currently in -mm which might be from bhe@xxxxxxxxxx are
mm-vmallocc-add-flags-to-mark-vm_map_ram-area.patch
mm-vmallocc-allow-vread-to-read-out-vm_map_ram-areas.patch
mm-vmalloc-explicitly-identify-vm_map_ram-area-when-shown-in-proc-vmcoreinfo.patch
mm-vmalloc-skip-the-uninitilized-vmalloc-areas.patch
powerpc-mm-add-vm_ioremap-flag-to-the-vmalloc-area.patch
sh-mm-set-vm_ioremap-flag-to-the-vmalloc-area.patch
