[PATCH][2.6] No swapping on memory backed swapfiles
From: Zwane Mwaikambo
Date: Mon Oct 13 2003 - 02:59:38 EST
This fixes an oops when running LTP on a system with a tmpfs /tmp. The
oops is from the lack of a readpage a_op. This patch simply disables
enabling of swap for memory backed swapfiles.
Unable to handle kernel NULL pointer dereference at virtual address 00000000
printing eip:
00000000
*pde = 00000000
Oops: 0000 [#1]
CPU: 0
EIP: 0060:[<00000000>] Not tainted
EFLAGS: 00010246
EIP is at 0x0
eax: 00000000 ebx: c1076458 ecx: c1651660 edx: c1076458
esi: 00000000 edi: e2c38f68 ebp: dfd93f24 esp: e202bf4c
ds: 007b es: 007b ss: 0068
Process swapon02 (pid: 5718, threadinfo=e202a000 task=d6f769d0)
Stack: c0145c0c e2c38f68 c1076458 dfd93e88 dfd93e88 00000000 00000000 c01658c8
dfd93f24 00000000 00000000 e2c38f68 e3d7fe58 c07430d0 dfd93e88 dfd93e88
00000000 00000001 00000000 00000000 ffffffea dfd93f24 e2c38f68 00000000
Call Trace:
[<c0145c0c>] read_cache_page+0x5c/0x360
[<c01658c8>] sys_swapon+0x528/0xa30
[<c01096e9>] sysenter_past_esp+0x52/0x79
Code: Bad EIP value.
(gdb) list *read_cache_page+0x5c
0xc0145c0c is in read_cache_page (mm/filemap.c:1393).
1388 page_cache_release(cached_page);
1389 return ERR_PTR(err);
1390 }
1391 page = cached_page;
1392 cached_page = NULL;
1393 err = filler(data, page);
1394 if (err < 0) {
1395 page_cache_release(page);
1396 page = ERR_PTR(err);
1397 }
Index: linux-2.6.0-test7/mm/swapfile.c
===================================================================
RCS file: /build/cvsroot/linux-2.6.0-test7/mm/swapfile.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 swapfile.c
--- linux-2.6.0-test7/mm/swapfile.c 9 Oct 2003 05:56:12 -0000 1.1.1.1
+++ linux-2.6.0-test7/mm/swapfile.c 13 Oct 2003 07:27:28 -0000
@@ -1233,6 +1233,7 @@ asmlinkage long sys_swapon(const char __
struct page *page = NULL;
struct inode *inode;
struct inode *downed_inode = NULL;
+ struct backing_dev_info *bdi;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -1293,6 +1294,10 @@ asmlinkage long sys_swapon(const char __
}
error = -EINVAL;
+ bdi = mapping->backing_dev_info;
+ if (bdi->memory_backed)
+ goto bad_swap;
+
if (S_ISBLK(inode->i_mode)) {
bdev = inode->i_bdev;
error = bd_claim(bdev, sys_swapon);
-
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