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Commit e81ce85f authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds
Browse files

mm, vmalloc: iterate vmap_area_list, instead of vmlist in vread/vwrite() 



Now, when we hold a vmap_area_lock, va->vm can't be discarded.  So we can
safely access to va->vm when iterating a vmap_area_list with holding a
vmap_area_lock.  With this property, change iterating vmlist codes in
vread/vwrite() to iterating vmap_area_list.

There is a little difference relate to lock, because vmlist_lock is mutex,
but, vmap_area_lock is spin_lock.  It may introduce a spinning overhead
during vread/vwrite() is executing.  But, these are debug-oriented
functions, so this overhead is not real problem for common case.

Signed-off-by: default avatarJoonsoo Kim <js1304@gmail.com>
Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c69480ad

mm/vmalloc.c

+32 −16
Original line number Diff line number Diff line
@@ -2012,7 +2012,8 @@ static int aligned_vwrite(char *buf, char *addr, unsigned long count) 


long vread(char *buf, char *addr, unsigned long count)

{

	struct vm_struct *tmp;

	struct vmap_area *va;

	struct vm_struct *vm;

	char *vaddr, *buf_start = buf;

	unsigned long buflen = count;

	unsigned long n;
@@ -2021,10 +2022,17 @@ long vread(char *buf, char *addr, unsigned long count) 
	if ((unsigned long) addr + count < count)

		count = -(unsigned long) addr;



	read_lock(&vmlist_lock);

	for (tmp = vmlist; count && tmp; tmp = tmp->next) {

		vaddr = (char *) tmp->addr;

		if (addr >= vaddr + tmp->size - PAGE_SIZE)

	spin_lock(&vmap_area_lock);

	list_for_each_entry(va, &vmap_area_list, list) {

		if (!count)

			break;



		if (!(va->flags & VM_VM_AREA))

			continue;



		vm = va->vm;

		vaddr = (char *) vm->addr;

		if (addr >= vaddr + vm->size - PAGE_SIZE)

			continue;

		while (addr < vaddr) {

			if (count == 0)
@@ -2034,10 +2042,10 @@ long vread(char *buf, char *addr, unsigned long count) 
			addr++;

			count--;

		}

		n = vaddr + tmp->size - PAGE_SIZE - addr;

		n = vaddr + vm->size - PAGE_SIZE - addr;

		if (n > count)

			n = count;

		if (!(tmp->flags & VM_IOREMAP))

		if (!(vm->flags & VM_IOREMAP))

			aligned_vread(buf, addr, n);

		else /* IOREMAP area is treated as memory hole */

			memset(buf, 0, n);
@@ -2046,7 +2054,7 @@ long vread(char *buf, char *addr, unsigned long count) 
		count -= n;

	}

finished:

	read_unlock(&vmlist_lock);

	spin_unlock(&vmap_area_lock);



	if (buf == buf_start)

		return 0;
@@ -2085,7 +2093,8 @@ finished: 


long vwrite(char *buf, char *addr, unsigned long count)

{

	struct vm_struct *tmp;

	struct vmap_area *va;

	struct vm_struct *vm;

	char *vaddr;

	unsigned long n, buflen;

	int copied = 0;
@@ -2095,10 +2104,17 @@ long vwrite(char *buf, char *addr, unsigned long count) 
		count = -(unsigned long) addr;

	buflen = count;



	read_lock(&vmlist_lock);

	for (tmp = vmlist; count && tmp; tmp = tmp->next) {

		vaddr = (char *) tmp->addr;

		if (addr >= vaddr + tmp->size - PAGE_SIZE)

	spin_lock(&vmap_area_lock);

	list_for_each_entry(va, &vmap_area_list, list) {

		if (!count)

			break;



		if (!(va->flags & VM_VM_AREA))

			continue;



		vm = va->vm;

		vaddr = (char *) vm->addr;

		if (addr >= vaddr + vm->size - PAGE_SIZE)

			continue;

		while (addr < vaddr) {

			if (count == 0)
@@ -2107,10 +2123,10 @@ long vwrite(char *buf, char *addr, unsigned long count) 
			addr++;

			count--;

		}

		n = vaddr + tmp->size - PAGE_SIZE - addr;

		n = vaddr + vm->size - PAGE_SIZE - addr;

		if (n > count)

			n = count;

		if (!(tmp->flags & VM_IOREMAP)) {

		if (!(vm->flags & VM_IOREMAP)) {

			aligned_vwrite(buf, addr, n);

			copied++;

		}
@@ -2119,7 +2135,7 @@ long vwrite(char *buf, char *addr, unsigned long count) 
		count -= n;

	}

finished:

	read_unlock(&vmlist_lock);

	spin_unlock(&vmap_area_lock);

	if (!copied)

		return 0;

	return buflen;