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authorMiklos Szeredi <mszeredi@suse.cz>2007-07-19 08:47:24 (GMT)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 17:04:41 (GMT)
commit3ee6dafc677a68e461a7ddafc94a580ebab80735 (patch)
tree6a92c9f5bd24ff80c52c944327c3b065234f7ad2 /mm/fremap.c
parentbb2d5ce16409efcdf94017a6b6fecd468226e29c (diff)
only allow nonlinear vmas for ram backed filesystems
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@suse.cz> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: William Lee Irwin III <wli@holomorphy.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/fremap.c')
-rw-r--r--mm/fremap.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/mm/fremap.c b/mm/fremap.c
index 5f50d73..c395b1a 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -181,6 +181,25 @@ asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
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;

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