Commit 53becf32 authored by Uladzislau Rezki (Sony)'s avatar Uladzislau Rezki (Sony) Committed by Andrew Morton
Browse files

mm: vmalloc: support multiple nodes in vread_iter 

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: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: default avatarBaoquan 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 96aa8437

mm/vmalloc.c

+53 −14
Original line number Diff line number Diff line
@@ -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);
@@ -4179,14 +4211,21 @@ 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:

	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. */

	if (vn)

		spin_unlock(&vn->busy.lock);



	return count - remains;