Messages in this thread Patch in this message | | | Date | Thu, 5 Jan 2006 13:18:57 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: Fw: crash on x86_64 - mm related? |
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On Thu, 5 Jan 2006, Ryan Richter wrote: > > Another one. I can't keep running this kernel - nearly all of our > backup tapes are erased now. If a drive were to fail today, we would > lose hundreds of GB of irreplacible data. I'm going back to 2.6.11.3 > until we have a full set of backups again.
Yeah, don't trash your backups.
If/when you try something again, how about these two trivial one-liners?
I'm not 100% sure the mapcount sanity check is strictly speaking right (no locking between mapcount/pagecount comparison), but the page count really should never fall below the mapcount, so aside from races that I don't think can be triggered in practice, this might be very useful to find where those pesky page counts suddenly disappear..
Right now we get the oops "too late" - something has decremented the page count way too far, but we don't know what it was, and the actual function that triggers it _seems_ to be harmless.
The other part of the patch is to clear "page" when it's being free'd, in case somebody tries to free the same thing twice. I don't see how that could happen either, but...
The patch is untested in every way. No guarantees.
Linus
--- diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c index c4aade8..18e60e1 100644 --- a/drivers/scsi/st.c +++ b/drivers/scsi/st.c @@ -4481,6 +4481,7 @@ static int sgl_unmap_user_pages(struct s for (i=0; i < nr_pages; i++) { struct page *page = sgl[i].page; + sgl[i].page = NULL; if (dirtied) SetPageDirty(page); /* FIXME: cache flush missing for rw==READ diff --git a/include/linux/mm.h b/include/linux/mm.h index a06a84d..daf504d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -299,6 +299,7 @@ struct page { #define put_page_testzero(p) \ ({ \ BUG_ON(page_count(p) == 0); \ + BUG_ON(page_count(p) <= page_mapcount(p)); \ atomic_add_negative(-1, &(p)->_count); \ }) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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