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SubjectRe: Regression - locking (all from 2.6.28)
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On Mon, 2009-03-02 at 12:11 -0800, Andrew Morton wrote:
> > Mar 1 00:06:51 localhost kernel: [ 74.008165] unreferenced object 0xf6c4daf0 (size 52):
> > Mar 1 00:06:51 localhost kernel: [ 74.008170] comm "swapper", pid 1, jiffies 4294893427
> > Mar 1 00:06:51 localhost kernel: [ 74.008175] backtrace:
> > Mar 1 00:06:51 localhost kernel: [ 74.008179] [<c018978c>] kmemleak_alloc+0x17e/0x28e
> > Mar 1 00:06:51 localhost kernel: [ 74.008185] [<c0186b86>] kmem_cache_alloc+0xdc/0xe7
> > Mar 1 00:06:51 localhost kernel: [ 74.008190] [<c01a53bd>] alloc_buffer_head+0x16/0x71
> > Mar 1 00:06:51 localhost kernel: [ 74.008196] [<c01a5b91>] alloc_page_buffers+0x23/0xad
> > Mar 1 00:06:51 localhost kernel: [ 74.008200] [<c01a5fd4>] __getblk+0x192/0x26b
> > Mar 1 00:06:51 localhost kernel: [ 74.008205] [<c01d91f4>] jread+0x105/0x1de
> > Mar 1 00:06:51 localhost kernel: [ 74.008209] [<c01d932b>] do_one_pass+0x5e/0x38c
> > Mar 1 00:06:51 localhost kernel: [ 74.008213] [<c01d96f8>] journal_recover+0x41/0x9d
> > Mar 1 00:06:51 localhost kernel: [ 74.008218] [<c01db8d4>] journal_load+0x47/0x7b
> > Mar 1 00:06:51 localhost kernel: [ 74.008221] [<c01d43d1>] ext3_fill_super+0xe9d/0x144c
> > Mar 1 00:06:51 localhost kernel: [ 74.008225] [<c018d721>] get_sb_bdev+0xfa/0x140
> > Mar 1 00:06:51 localhost kernel: [ 74.008231] [<c01d2070>] ext3_get_sb+0x18/0x1a
> > Mar 1 00:06:51 localhost kernel: [ 74.008235] [<c018c71f>] vfs_kern_mount+0x41/0x7c
> > Mar 1 00:06:51 localhost kernel: [ 74.008241] [<c018c7a8>] do_kern_mount+0x37/0xbe
> > Mar 1 00:06:51 localhost kernel: [ 74.008247] [<c019f0bf>] do_mount+0x5f7/0x630
> > Mar 1 00:06:51 localhost kernel: [ 74.008253] [<c019f167>] sys_mount+0x6f/0xac
>
> I suspect kmemleak has gone nuts here.

It seems that the buffer_head structure allocated above is stored in
page->private. However, the page structures are no longer scanned in
newer versions of kmemleak. That's the hunk that was removed after
comments about the contiguity of a node's memory:

+ /* mem_map scanning */
+ for_each_online_node(i) {
+ struct page *page, *end;
+
+ page = NODE_MEM_MAP(i);
+ end = page + NODE_DATA(i)->node_spanned_pages;
+
+ scan_block(page, end, NULL);
+ }

The alternative is to inform kmemleak about the page structures returned
from __alloc_pages_internal() but there would be problems with recursive
calls into kmemleak when it allocates its own data structures.

I'll look at re-adding the hunk above, maybe with some extra checks like
pfn_valid().

> kmemleak has no MAINTAINERS entry, btw.

The entry is called "KERNEL MEMORY LEAK DETECTOR" but it makes sense to
change it to KMEMLEAK.

Thanks.

--
Catalin



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