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authorLinus Torvalds <torvalds@g5.osdl.org>2005-12-11 22:46:02 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2005-12-11 22:46:02 -0500
commitfb155c1619f056ae9765eed272cd6aba6e1a7399 (patch)
tree04a82b5fbf83bdb9dcf7fec9aeaaecf92532d88c
parente4f5c82a92c2a546a16af1614114eec19120e40a (diff)
Allow arbitrary shared PFNMAP's
A shared mapping doesn't cause COW-pages, so we don't need to worry about the whole vm_pgoff logic to decide if a PFN-remapped page has gone through COW or not. This makes it possible to entirely avoid the special "partial remapping" logic for the common case. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--mm/memory.c16
1 files changed, 12 insertions, 4 deletions
diff --git a/mm/memory.c b/mm/memory.c
index aa8af0e20269..e65f8fc8ea67 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -377,6 +377,8 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, pte_
377 unsigned long off = (addr - vma->vm_start) >> PAGE_SHIFT; 377 unsigned long off = (addr - vma->vm_start) >> PAGE_SHIFT;
378 if (pfn == vma->vm_pgoff + off) 378 if (pfn == vma->vm_pgoff + off)
379 return NULL; 379 return NULL;
380 if (vma->vm_flags & VM_SHARED)
381 return NULL;
380 } 382 }
381 383
382 /* 384 /*
@@ -1343,9 +1345,6 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1343 struct mm_struct *mm = vma->vm_mm; 1345 struct mm_struct *mm = vma->vm_mm;
1344 int err; 1346 int err;
1345 1347
1346 if (addr != vma->vm_start || end != vma->vm_end)
1347 return incomplete_pfn_remap(vma, addr, end, pfn, prot);
1348
1349 /* 1348 /*
1350 * Physically remapped pages are special. Tell the 1349 * Physically remapped pages are special. Tell the
1351 * rest of the world about it: 1350 * rest of the world about it:
@@ -1359,9 +1358,18 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1359 * VM_PFNMAP tells the core MM that the base pages are just 1358 * VM_PFNMAP tells the core MM that the base pages are just
1360 * raw PFN mappings, and do not have a "struct page" associated 1359 * raw PFN mappings, and do not have a "struct page" associated
1361 * with them. 1360 * with them.
1361 *
1362 * There's a horrible special case to handle copy-on-write
1363 * behaviour that some programs depend on. We mark the "original"
1364 * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1362 */ 1365 */
1366 if (!(vma->vm_flags & VM_SHARED)) {
1367 if (addr != vma->vm_start || end != vma->vm_end)
1368 return incomplete_pfn_remap(vma, addr, end, pfn, prot);
1369 vma->vm_pgoff = pfn;
1370 }
1371
1363 vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP; 1372 vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
1364 vma->vm_pgoff = pfn;
1365 1373
1366 BUG_ON(addr >= end); 1374 BUG_ON(addr >= end);
1367 pfn -= addr >> PAGE_SHIFT; 1375 pfn -= addr >> PAGE_SHIFT;