From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hugh Dickins Date: Fri, 03 Mar 2006 05:18:51 +0000 Subject: Re: hugepage: Fix hugepage logic in free_pgtables() harder Message-Id: List-Id: References: <20060303010408.GG23766@localhost.localdomain> In-Reply-To: <20060303010408.GG23766@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: 'David Gibson' Cc: Andrew Morton , "Chen, Kenneth W" , William Irwin , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org On Fri, 3 Mar 2006, 'David Gibson' wrote: > Sigh. Turns out the hugepage logic in free_pgtables() was doubly > broken. The loop coalescing multiple normal page VMAs into one call > to free_pgd_range() had an off by one error, which could mean it would > coalesce one hugepage VMA into the same bundle (checking 'vma' not > 'next' in the loop). I transferred this bug into the new > is_vm_hugetlb_page() based version. Here's the fix. > > This one didn't bite on powerpc previously for the same reason the > is_hugepage_only_range() problem didn't: powerpc's > hugetlb_free_pgd_range() is identical to free_pgd_range(). It didn't > bite on ia64 because the hugepage region is distant enough from any > other region that the separated PMD_SIZE distance test would always > prevent coalescing the two together. I agree with your patch, but not with your comment: it's just a fix to your earlier patch, there's no such off-by-one in the mainline free_pgtables. Probably you were misled by my use of "vma->vm_mm" rather than "next->vm_mm", equal but admittedly confusing, when looking at the "next" vma. Hugh