Messages in this thread Patch in this message | | | Date | Tue, 6 Jun 2006 19:15:21 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: 2.6.17-rc5-mm1 |
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On Tue, 6 Jun 2006, Martin Schwidefsky wrote: > On Tue, 2006-06-06 at 18:59 +0100, Hugh Dickins wrote: > > Even s390 is okay, isn't it? MartinS's swp_type returns the highest > > type, 31, corresponding to 32 types, as on every other architecture. > > You and I and Martin Bligh would prefer this patch... > > As long as nobody will have the smart idea to increase MAX_SWAPFILES to > more than 32 I'm fine with it.
Thanks, Martin: we know very well that we cannot increase MAX_SWAPFILES without going through all the architectures adjusting their swap ptes (and maybe making MAX_SWAPFILES_SHIFT per-arch), so I don't see any problem there. But Christoph has observed that the comment becomes out-of-date, so updated patch (adding your ack) below...
Remove unnecessary obfuscation from sys_swapon's range check on swap type, which blew up causing memory corruption once swapless migration made MAX_SWAPFILES no longer 2 ^ MAX_SWAPFILES_SHIFT.
Signed-off-by: Hugh Dickins <hugh@veritas.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
--- 2.6.17-rc5-mm3/mm/swapfile.c 2006-06-04 11:52:47.000000000 +0100 +++ linux/mm/swapfile.c 2006-06-06 19:08:51.000000000 +0100 @@ -1392,19 +1392,7 @@ asmlinkage long sys_swapon(const char __ if (!(p->flags & SWP_USED)) break; error = -EPERM; - /* - * Test if adding another swap device is possible. There are - * two limiting factors: 1) the number of bits for the swap - * type swp_entry_t definition and 2) the number of bits for - * the swap type in the swap ptes as defined by the different - * architectures. To honor both limitations a swap entry - * with swap offset 0 and swap type ~0UL is created, encoded - * to a swap pte, decoded to a swp_entry_t again and finally - * the swap type part is extracted. This will mask all bits - * from the initial ~0UL that can't be encoded in either the - * swp_entry_t or the architecture definition of a swap pte. - */ - if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) { + if (type >= MAX_SWAPFILES) { spin_unlock(&swap_lock); goto out; } - 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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