+ mm-vmallocc-add-used_map-into-vmap_block-to-track-space-of-vmap_block.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/vmalloc.c: add used_map into vmap_block to track space of vmap_block
has been added to the -mm mm-unstable branch.  Its filename is
     mm-vmallocc-add-used_map-into-vmap_block-to-track-space-of-vmap_block.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmallocc-add-used_map-into-vmap_block-to-track-space-of-vmap_block.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Baoquan He <bhe@redhat.com>
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@oracle.com/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 preparatoin for later use.

Link: https://lkml.kernel.org/r/20230113031921.64716-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20230113031921.64716-2-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Reported-by: Stephen Brennan <stephen.s.brennan@oracle.com>
  Link: https://lore.kernel.org/all/87ilk6gos2.fsf@oracle.com/T/#u
Cc: Baoquan He <bhe@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- 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@redhat.com are

mm-vmallocc-add-used_map-into-vmap_block-to-track-space-of-vmap_block.patch
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