On Sunday 29 May 2011 18:23:46 Nai Xia wrote: > On Sunday 29 May 2011 04:17:04 Hugh Dickins wrote: > > I've hit the "address >= vma->vm_end" check in do_page_add_anon_rmap() > > just once. The stack showed khugepaged allocation trying to compact > > pages: the call to page_add_anon_rmap() coming from remove_migration_pte(). > > > > That path holds anon_vma lock, but does not hold mmap_sem: it can > > therefore race with a split_vma(), and in commit 5f70b962ccc2 "mmap: > > avoid unnecessary anon_vma lock" we just took away the anon_vma lock > > protection when adjusting vma->vm_end. > > > > I don't think that particular BUG_ON ever caught anything interesting, > > so better replace it by a comment, than reinstate the anon_vma locking. > > Is there another racing between "vma->vm_pgoff = pgoff;" in > vma_adjust() and linear_page_index() in __page_set_anon_rmap() ? Oh, sorry, please ignore this, this _is_ protected by anon_vma lock. Nai Xia > > > Nai Xia > > > > > Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> > > --- > > mm/rmap.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > --- linux.orig/mm/rmap.c 2011-05-27 19:05:27.000000000 -0700 > > +++ linux/mm/rmap.c 2011-05-27 20:07:44.601361236 -0700 > > @@ -1014,7 +1014,7 @@ void do_page_add_anon_rmap(struct page * > > return; > > > > VM_BUG_ON(!PageLocked(page)); > > - VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); > > + /* address might be in next vma when migration races vma_adjust */ > > if (first) > > __page_set_anon_rmap(page, vma, address, exclusive); > > else > > @@ -1709,7 +1709,7 @@ void hugepage_add_anon_rmap(struct page > > > > BUG_ON(!PageLocked(page)); > > BUG_ON(!anon_vma); > > - BUG_ON(address < vma->vm_start || address >= vma->vm_end); > > + /* address might be in next vma when migration races vma_adjust */ > > first = atomic_inc_and_test(&page->_mapcount); > > if (first) > > __hugepage_set_anon_rmap(page, vma, address, 0); > > > > -- > > To unsubscribe, send a message with 'unsubscribe linux-mm' in > > the body to majordomo@xxxxxxxxxx For more info on Linux MM, > > see: http://www.linux-mm.org/ . > > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>