From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 58394211DBE72 for ; Wed, 13 Mar 2019 02:58:36 -0700 (PDT) Date: Wed, 13 Mar 2019 10:58:34 +0100 From: Jan Kara Subject: Re: [PATCH v2] fs/dax: deposit pagetable even when installing zero page Message-ID: <20190313095834.GF32521@quack2.suse.cz> References: <20190309120721.21416-1-aneesh.kumar@linux.ibm.com> <8736nrnzxm.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <8736nrnzxm.fsf@linux.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: "Aneesh Kumar K.V" Cc: Jan Kara , linux-nvdimm@lists.01.org, linux-mm@kvack.org, Alexander Viro , Ross Zwisler , linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, akpm@linux-foundation.org List-ID: On Wed 13-03-19 10:17:17, Aneesh Kumar K.V wrote: > > Hi Dan/Andrew/Jan, > > "Aneesh Kumar K.V" writes: > > > 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 > > > > Fixes: b5beae5e224f ("powerpc/pseries: Add driver for PAPR SCM regions") > > Reviewed-by: Jan Kara > > Signed-off-by: Aneesh Kumar K.V > > Any suggestion on which tree this patch should got to? Also since this > fix a kernel crash, we may want to get this to 5.1? I think this should go through Dan's tree... Honza > > --- > > Changes from v1: > > * Add reviewed-by: > > * Add Fixes: > > > > 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 > > -aneesh > -- Jan Kara SUSE Labs, CR _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm