The patch titled
only allow nonlinear vmas for ram backed filesystems
has been added to the -mm tree. Its filename is
only-allow-nonlinear-vmas-for-ram-backed-filesystems.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: only allow nonlinear vmas for ram backed filesystems
From: Miklos Szeredi <mszeredi@xxxxxxx>
page_mkclean() doesn't re-protect ptes for non-linear mappings, so a later
re-dirty through such a mapping will not generate a fault, PG_dirty will
not reflect the dirty state and the dirty count will be skewed. This
implies that msync() is also currently broken for nonlinear mappings.
The easiest solution is to emulate remap_file_pages on non-linear mappings
with simple mmap() for non ram-backed filesystems. Applications continue
to work (albeit slower), as long as the number of remappings remain below
the maximum vma count.
However all currently known real uses of non-linear mappings are for ram
backed filesystems, which this patch doesn't affect.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: William Lee Irwin III <wli@xxxxxxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/fremap.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff -puN mm/fremap.c~only-allow-nonlinear-vmas-for-ram-backed-filesystems mm/fremap.c
--- a/mm/fremap.c~only-allow-nonlinear-vmas-for-ram-backed-filesystems
+++ a/mm/fremap.c
@@ -181,6 +181,24 @@ asmlinkage long sys_remap_file_pages(uns
goto retry;
}
mapping = vma->vm_file->f_mapping;
+ /*
+ * page_mkclean doesn't work on nonlinear vmas, so if dirty
+ * pages need to be accounted, emulate with linear vmas.
+ */
+ if (mapping_cap_account_dirty(mapping)) {
+ unsigned long addr;
+
+ flags &= MAP_NONBLOCK;
+ addr = mmap_region(vma->vm_file, start, size, flags,
+ vma->vm_flags, pgoff, 1);
+ if (IS_ERR_VALUE(addr))
+ err = addr;
+ else {
+ BUG_ON(addr != start);
+ err = 0;
+ }
+ goto out;
+ }
spin_lock(&mapping->i_mmap_lock);
flush_dcache_mmap_lock(mapping);
vma->vm_flags |= VM_NONLINEAR;
_
Patches currently in -mm which might be from mszeredi@xxxxxxx are
fuse-validate-rootmode-mount-option.patch
split-mmap.patch
only-allow-nonlinear-vmas-for-ram-backed-filesystems.patch
fix-quadratic-behavior-of-shrink_dcache_parent.patch
mm-shrink-parent-dentries-when-shrinking-slab.patch
add-filesystem-subtype-support.patch
add-file-position-info-to-proc.patch
add-file-position-info-to-proc-fix.patch
consolidate-generic_writepages-and-mpage_writepages.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
