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authorBaoquan He <bhe@redhat.com>2023-02-06 09:40:14 +0100
committerAndrew Morton <akpm@linux-foundation.org>2023-02-10 01:51:42 +0100
commitd76f99548cf0474c3bf75f25fab1778e03ade5f2 (patch)
tree6eae85b0fc673feb88756319942418e6a42ea265 /mm/vmalloc.c
parentshmem: fix W=1 build warnings with CONFIG_SHMEM=n (diff)
downloadlinux-d76f99548cf0474c3bf75f25fab1778e03ade5f2.tar.xz
linux-d76f99548cf0474c3bf75f25fab1778e03ade5f2.zip
mm/vmalloc.c: add used_map into vmap_block to track space of vmap_block
Patch series "mm/vmalloc.c: allow vread() to read out vm_map_ram areas", v5. 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. 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/20230206084020.174506-1-bhe@redhat.com Link: https://lkml.kernel.org/r/20230206084020.174506-2-bhe@redhat.com Signed-off-by: Baoquan He <bhe@redhat.com> Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Dan Carpenter <error27@gmail.com> Cc: Stephen Brennan <stephen.s.brennan@oracle.com> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to '')
-rw-r--r--mm/vmalloc.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1dd7ca258a76..0f1396d6fbe6 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1910,6 +1910,7 @@ 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;
@@ -1986,10 +1987,12 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
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);
@@ -2099,6 +2102,7 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
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);
@@ -2132,6 +2136,9 @@ static void vb_free(unsigned long addr, unsigned long size)
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);