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: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
c69480adee
commit
e81ce85f96
48
mm/vmalloc.c
48
mm/vmalloc.c
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@ -2012,7 +2012,8 @@ static int aligned_vwrite(char *buf, char *addr, unsigned long count)
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long vread(char *buf, char *addr, unsigned long count)
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{
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struct vm_struct *tmp;
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struct vmap_area *va;
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struct vm_struct *vm;
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char *vaddr, *buf_start = buf;
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unsigned long buflen = count;
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unsigned long n;
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@ -2021,10 +2022,17 @@ long vread(char *buf, char *addr, unsigned long count)
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if ((unsigned long) addr + count < count)
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count = -(unsigned long) addr;
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read_lock(&vmlist_lock);
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for (tmp = vmlist; count && tmp; tmp = tmp->next) {
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vaddr = (char *) tmp->addr;
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if (addr >= vaddr + tmp->size - PAGE_SIZE)
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spin_lock(&vmap_area_lock);
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list_for_each_entry(va, &vmap_area_list, list) {
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if (!count)
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break;
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if (!(va->flags & VM_VM_AREA))
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continue;
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vm = va->vm;
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vaddr = (char *) vm->addr;
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if (addr >= vaddr + vm->size - PAGE_SIZE)
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continue;
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while (addr < vaddr) {
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if (count == 0)
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@ -2034,10 +2042,10 @@ long vread(char *buf, char *addr, unsigned long count)
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addr++;
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count--;
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}
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n = vaddr + tmp->size - PAGE_SIZE - addr;
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n = vaddr + vm->size - PAGE_SIZE - addr;
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if (n > count)
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n = count;
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if (!(tmp->flags & VM_IOREMAP))
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if (!(vm->flags & VM_IOREMAP))
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aligned_vread(buf, addr, n);
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else /* IOREMAP area is treated as memory hole */
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memset(buf, 0, n);
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@ -2046,7 +2054,7 @@ long vread(char *buf, char *addr, unsigned long count)
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count -= n;
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}
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finished:
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read_unlock(&vmlist_lock);
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spin_unlock(&vmap_area_lock);
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if (buf == buf_start)
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return 0;
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@ -2085,7 +2093,8 @@ finished:
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long vwrite(char *buf, char *addr, unsigned long count)
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{
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struct vm_struct *tmp;
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struct vmap_area *va;
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struct vm_struct *vm;
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char *vaddr;
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unsigned long n, buflen;
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int copied = 0;
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@ -2095,10 +2104,17 @@ long vwrite(char *buf, char *addr, unsigned long count)
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count = -(unsigned long) addr;
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buflen = count;
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read_lock(&vmlist_lock);
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for (tmp = vmlist; count && tmp; tmp = tmp->next) {
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vaddr = (char *) tmp->addr;
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if (addr >= vaddr + tmp->size - PAGE_SIZE)
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spin_lock(&vmap_area_lock);
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list_for_each_entry(va, &vmap_area_list, list) {
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if (!count)
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break;
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if (!(va->flags & VM_VM_AREA))
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continue;
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vm = va->vm;
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vaddr = (char *) vm->addr;
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if (addr >= vaddr + vm->size - PAGE_SIZE)
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continue;
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while (addr < vaddr) {
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if (count == 0)
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@ -2107,10 +2123,10 @@ long vwrite(char *buf, char *addr, unsigned long count)
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addr++;
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count--;
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}
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n = vaddr + tmp->size - PAGE_SIZE - addr;
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n = vaddr + vm->size - PAGE_SIZE - addr;
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if (n > count)
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n = count;
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if (!(tmp->flags & VM_IOREMAP)) {
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if (!(vm->flags & VM_IOREMAP)) {
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aligned_vwrite(buf, addr, n);
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copied++;
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}
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@ -2119,7 +2135,7 @@ long vwrite(char *buf, char *addr, unsigned long count)
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count -= n;
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}
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finished:
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read_unlock(&vmlist_lock);
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spin_unlock(&vmap_area_lock);
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if (!copied)
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return 0;
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return buflen;
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