Commit 08f26bb2 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds

[PATCH] mm: truncate SMP race fix

Fix up an smp race introduced in 2.6.11-rc1
Signed-off-by: default avatarAndrea Arcangeli <andrea@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4adb12fc
......@@ -1556,8 +1556,17 @@ void unmap_mapping_range(struct address_space *mapping,
spin_lock(&mapping->i_mmap_lock);
/* serialize i_size write against truncate_count write */
smp_wmb();
/* Protect against page faults, and endless unmapping loops */
mapping->truncate_count++;
/*
* For archs where spin_lock has inclusive semantics like ia64
* this smp_mb() will prevent to read pagetable contents
* before the truncate_count increment is visible to
* other cpus.
*/
smp_mb();
if (unlikely(is_restart_addr(mapping->truncate_count))) {
if (mapping->truncate_count == 0)
reset_vma_truncate_counts(mapping);
......@@ -1865,10 +1874,18 @@ do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;
sequence = mapping->truncate_count;
smp_rmb(); /* serializes i_size against truncate_count */
}
retry:
cond_resched();
new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, &ret);
/*
* No smp_rmb is needed here as long as there's a full
* spin_lock/unlock sequence inside the ->nopage callback
* (for the pagecache lookup) that acts as an implicit
* smp_mb() and prevents the i_size read to happen
* after the next truncate_count read.
*/
/* no page was available -- either SIGBUS or OOM */
if (new_page == NOPAGE_SIGBUS)
......
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