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[195.135.220.15]) by mx.google.com with ESMTPS id p18si3901839ejj.234.2019.02.28.01.21.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Feb 2019 01:21:03 -0800 (PST) Received-SPF: pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jack@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4904DAC5A; Thu, 28 Feb 2019 09:21:02 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E00081E4263; Thu, 28 Feb 2019 10:21:01 +0100 (CET) Date: Thu, 28 Feb 2019 10:21:01 +0100 From: Jan Kara To: "Aneesh Kumar K.V" Cc: akpm@linux-foundation.org, "Kirill A . Shutemov" , Jan Kara , mpe@ellerman.id.au, Ross Zwisler , Oliver O'Halloran , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 1/2] fs/dax: deposit pagetable even when installing zero page Message-ID: <20190228092101.GA22210@quack2.suse.cz> References: <20190228083522.8189-1-aneesh.kumar@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190228083522.8189-1-aneesh.kumar@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu 28-02-19 14:05:21, Aneesh Kumar K.V wrote: > Architectures like ppc64 use the deposited page table to store hardware > page table slot information. Make sure we deposit a page table when > using zero page at the pmd level for hash. > > Without this we hit > > Unable to handle kernel paging request for data at address 0x00000000 > Faulting instruction address: 0xc000000000082a74 > Oops: Kernel access of bad area, sig: 11 [#1] > .... > > NIP [c000000000082a74] __hash_page_thp+0x224/0x5b0 > LR [c0000000000829a4] __hash_page_thp+0x154/0x5b0 > Call Trace: > hash_page_mm+0x43c/0x740 > do_hash_page+0x2c/0x3c > copy_from_iter_flushcache+0xa4/0x4a0 > pmem_copy_from_iter+0x2c/0x50 [nd_pmem] > dax_copy_from_iter+0x40/0x70 > dax_iomap_actor+0x134/0x360 > iomap_apply+0xfc/0x1b0 > dax_iomap_rw+0xac/0x130 > ext4_file_write_iter+0x254/0x460 [ext4] > __vfs_write+0x120/0x1e0 > vfs_write+0xd8/0x220 > SyS_write+0x6c/0x110 > system_call+0x3c/0x130 > > Signed-off-by: Aneesh Kumar K.V Thanks for the patch. It looks good to me. You can add: Reviewed-by: Jan Kara > --- > TODO: > * Add fixes tag Probably this is a problem since initial PPC PMEM support, isn't it? Honza > > fs/dax.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/fs/dax.c b/fs/dax.c > index 6959837cc465..01bfb2ac34f9 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -33,6 +33,7 @@ > #include > #include > #include > +#include > #include "internal.h" > > #define CREATE_TRACE_POINTS > @@ -1410,7 +1411,9 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, > { > struct address_space *mapping = vmf->vma->vm_file->f_mapping; > unsigned long pmd_addr = vmf->address & PMD_MASK; > + struct vm_area_struct *vma = vmf->vma; > struct inode *inode = mapping->host; > + pgtable_t pgtable = NULL; > struct page *zero_page; > spinlock_t *ptl; > pmd_t pmd_entry; > @@ -1425,12 +1428,22 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, > *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, > DAX_PMD | DAX_ZERO_PAGE, false); > > + if (arch_needs_pgtable_deposit()) { > + pgtable = pte_alloc_one(vma->vm_mm); > + if (!pgtable) > + return VM_FAULT_OOM; > + } > + > ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); > if (!pmd_none(*(vmf->pmd))) { > spin_unlock(ptl); > goto fallback; > } > > + if (pgtable) { > + pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); > + mm_inc_nr_ptes(vma->vm_mm); > + } > pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot); > pmd_entry = pmd_mkhuge(pmd_entry); > set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry); > @@ -1439,6 +1452,8 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, > return VM_FAULT_NOPAGE; > > fallback: > + if (pgtable) > + pte_free(vma->vm_mm, pgtable); > trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, *entry); > return VM_FAULT_FALLBACK; > } > -- > 2.20.1 > -- Jan Kara SUSE Labs, CR