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author | Baoquan He <bhe@redhat.com> | 2023-02-06 09:40:14 +0100 |
---|---|---|
committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-10 01:51:42 +0100 |
commit | d76f99548cf0474c3bf75f25fab1778e03ade5f2 (patch) | |
tree | 6eae85b0fc673feb88756319942418e6a42ea265 /mm/vmalloc.c | |
parent | shmem: fix W=1 build warnings with CONFIG_SHMEM=n (diff) | |
download | linux-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.c | 7 |
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); |