fs/dax: Deposit pagetable even when installing zero page

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")
Cc: <stable@vger.kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/fs/dax.c b/fs/dax.c
index ca0671d55aa699df6723ffb897706b6579c68780..e5e54da1715f630cf1471e625e72045b6f31e112 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -33,6 +33,7 @@
 #include <linux/sizes.h>
 #include <linux/mmu_notifier.h>
 #include <linux/iomap.h>
+#include <asm/pgalloc.h>
 #include "internal.h"
 
 #define CREATE_TRACE_POINTS
@@ -1407,7 +1408,9 @@ 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;
@@ -1422,12 +1425,22 @@ 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);
@@ -1436,6 +1449,8 @@ 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;
 }