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Subject[RFC][PATCH] Fix for latent bug in vmtruncate()
The vmtruncate() function shifts down by PAGE_CACHE_SHIFT, then
calls vmtruncate_list(), which deals in terms of PAGE_SHIFT
instead. Currently, no harm done, since PAGE_CACHE_SHIFT and
PAGE_SHIFT are identical. Some day they might not be, hence
this patch.

I also took the liberty of modifying a hand-coded "if" that
seems to optimize for files that are not mapped to instead
use unlikely().


Thanx, Paul

diff -urN -X dontdiff linux-2.5.69/mm/memory.c linux-2.5.69.vmtruncate/mm/memory.c
--- linux-2.5.69/mm/memory.c Sun May 4 16:53:14 2003
+++ linux-2.5.69.vmtruncate/mm/memory.c Fri May 9 17:29:02 2003
@@ -1108,17 +1108,12 @@
if (inode->i_size < offset)
goto do_expand;
inode->i_size = offset;
+ pgoff = (offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
- if (list_empty(&mapping->i_mmap) && list_empty(&mapping->i_mmap_shared))
- goto out_unlock;
- pgoff = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- if (!list_empty(&mapping->i_mmap))
+ if (unlikely(!list_empty(&mapping->i_mmap)))
vmtruncate_list(&mapping->i_mmap, pgoff);
- if (!list_empty(&mapping->i_mmap_shared))
+ if (unlikely(!list_empty(&mapping->i_mmap_shared)))
vmtruncate_list(&mapping->i_mmap_shared, pgoff);
truncate_inode_pages(mapping, offset);
goto out_truncate;
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