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mm: vmalloc: support multiple nodes in vread_iter

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Extend the vread_iter() to be able to perform a sequential reading of VAs
which are spread among multiple nodes.  So a data read over the /dev/kmem
correctly reflects a vmalloc memory layout.

Link: https://lkml.kernel.org/r/20240102184633.748113-9-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Kazuhito Hagio <k-hagio-ab@nec.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Uladzislau Rezki (Sony) 2024-01-02 19:46:30 +01:00 committed by Andrew Morton
parent 96aa8437d1
commit 53becf32ae
1 changed files with 53 additions and 14 deletions
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67
mm/vmalloc.c
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@ -906,7 +906,7 @@ unsigned long vmalloc_nr_pages(void)
/* Look up the first VA which satisfies addr < va_end, NULL if none. */
static struct vmap_area *
find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root)
__find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root)
{
struct vmap_area *va = NULL;
struct rb_node *n = root->rb_node;
@ -930,6 +930,41 @@ find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root)
return va;
}
/*
* Returns a node where a first VA, that satisfies addr < va_end, resides.
* If success, a node is locked. A user is responsible to unlock it when a
* VA is no longer needed to be accessed.
*
* Returns NULL if nothing found.
*/
static struct vmap_node *
find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va)
{
struct vmap_node *vn, *va_node = NULL;
struct vmap_area *va_lowest;
int i;
for (i = 0; i < nr_vmap_nodes; i++) {
vn = &vmap_nodes[i];
spin_lock(&vn->busy.lock);
va_lowest = __find_vmap_area_exceed_addr(addr, &vn->busy.root);
if (va_lowest) {
if (!va_node || va_lowest->va_start < (*va)->va_start) {
if (va_node)
spin_unlock(&va_node->busy.lock);
*va = va_lowest;
va_node = vn;
continue;
}
}
spin_unlock(&vn->busy.lock);
}
return va_node;
}
static struct vmap_area *__find_vmap_area(unsigned long addr, struct rb_root *root)
{
struct rb_node *n = root->rb_node;
@ -4102,6 +4137,7 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
struct vm_struct *vm;
char *vaddr;
size_t n, size, flags, remains;
unsigned long next;
addr = kasan_reset_tag(addr);
@ -4111,19 +4147,15 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
remains = count;
/* Hooked to node_0 so far. */
vn = addr_to_node(0);
spin_lock(&vn->busy.lock);
va = find_vmap_area_exceed_addr((unsigned long)addr, &vn->busy.root);
if (!va)
vn = find_vmap_area_exceed_addr_lock((unsigned long) addr, &va);
if (!vn)
goto finished_zero;
/* no intersects with alive vmap_area */
if ((unsigned long)addr + remains <= va->va_start)
goto finished_zero;
list_for_each_entry_from(va, &vn->busy.head, list) {
do {
size_t copied;
if (remains == 0)
@ -4138,10 +4170,10 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
WARN_ON(flags == VMAP_BLOCK);
if (!vm && !flags)
continue;
goto next_va;
if (vm && (vm->flags & VM_UNINITIALIZED))
continue;
goto next_va;
/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
smp_rmb();
@ -4150,7 +4182,7 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
size = vm ? get_vm_area_size(vm) : va_size(va);
if (addr >= vaddr + size)
continue;
goto next_va;
if (addr < vaddr) {
size_t to_zero = min_t(size_t, vaddr - addr, remains);
@ -4179,15 +4211,22 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
if (copied != n)
goto finished;
}
next_va:
next = va->va_end;
spin_unlock(&vn->busy.lock);
} while ((vn = find_vmap_area_exceed_addr_lock(next, &va)));
finished_zero:
spin_unlock(&vn->busy.lock);
if (vn)
spin_unlock(&vn->busy.lock);
/* zero-fill memory holes */
return count - remains + zero_iter(iter, remains);
finished:
/* Nothing remains, or We couldn't copy/zero everything. */
spin_unlock(&vn->busy.lock);
if (vn)
spin_unlock(&vn->busy.lock);
return count - remains;
}