Re: [PATCH v3 02/10] fsdax: Factor helper: dax_fault_actor()
> + if (!pmd) > + return dax_load_hole(xas, mapping, , vmf); > + else > + return dax_pmd_load_hole(xas, vmf, iomap, ); > + if (pmd) > + return vmf_insert_pfn_pmd(vmf, pfn, write); > + if (write) > + return vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn); > + else > + return vmf_insert_mixed(vmf->vma, vmf->address, pfn); > +} No need for else statements after returning. Otherwise looks good: Reviewed-by: Christoph Hellwig
RE: [PATCH v3 02/10] fsdax: Factor helper: dax_fault_actor()
> -Original Message-
> From: Ritesh Harjani
> Sent: Tuesday, March 23, 2021 11:48 PM
> Subject: Re: [PATCH v3 02/10] fsdax: Factor helper: dax_fault_actor()
>
>
>
> On 3/19/21 7:22 AM, Shiyang Ruan wrote:
> > The core logic in the two dax page fault functions is similar. So,
> > move the logic into a common helper function. Also, to facilitate the
> > addition of new features, such as CoW, switch-case is no longer used
> > to handle different iomap types.
> >
> > Signed-off-by: Shiyang Ruan
> > ---
> > fs/dax.c | 291 +++
> > 1 file changed, 145 insertions(+), 146 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 7031e4302b13..33ddad0f3091 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -1053,6 +1053,66 @@ static vm_fault_t dax_load_hole(struct xa_state
> *xas,
> > return ret;
> > }
> >
> > +#ifdef CONFIG_FS_DAX_PMD
> > +static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault
> *vmf,
> > + struct iomap *iomap, void **entry)
> > +{
> > + 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;
> > + pfn_t pfn;
> > +
> > + zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
> > +
> > + if (unlikely(!zero_page))
> > + goto fallback;
> > +
> > + pfn = page_to_pfn_t(zero_page);
> > + *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);
> > + spin_unlock(ptl);
> > + trace_dax_pmd_load_hole(inode, vmf, zero_page, *entry);
> > + 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;
> > +}
> > +#else
> > +static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault
> *vmf,
> > + struct iomap *iomap, void **entry)
> > +{
> > + return VM_FAULT_FALLBACK;
> > +}
> > +#endif /* CONFIG_FS_DAX_PMD */
> > +
> > s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
> > {
> > sector_t sector = iomap_sector(iomap, pos & PAGE_MASK); @@
> -1289,6
> > +1349,61 @@ static int dax_fault_cow_page(struct vm_fault *vmf, struct
> iomap *iomap,
> > return 0;
> > }
> >
> > +/**
> > + * dax_fault_actor - Common actor to handle pfn insertion in PTE/PMD fault.
> > + * @vmf: vm fault instance
> > + * @pfnp: pfn to be returned
> > + * @xas: the dax mapping tree of a file
> > + * @entry: an unlocked dax entry to be inserted
> > + * @pmd: distinguish whether it is a pmd fault
> > + * @flags: iomap flags
> > + * @iomap: from iomap_begin()
> > + * @srcmap:from iomap_begin(), not equal to iomap if it is a CoW
> > + */
> > +static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp,
> > + struct xa_state *xas, void *entry, bool pmd, unsigned int flags,
> > + struct iomap *iomap, struct iomap *srcmap) {
> > + struct address_space *mapping = vmf->vma->vm_file->f_mapping;
> > + size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
> > + loff_t pos = (loff_t)xas->xa_offset << PAGE_SHIFT;
>
> shouldn't we use xa_index here for pos ?
> (loff_t)xas->xa_index << PAGE_SHIFT;
Yes.
>
> > + bool writ
Re: [PATCH v3 02/10] fsdax: Factor helper: dax_fault_actor()
On 3/19/21 7:22 AM, Shiyang Ruan wrote:
The core logic in the two dax page fault functions is similar. So, move
the logic into a common helper function. Also, to facilitate the
addition of new features, such as CoW, switch-case is no longer used to
handle different iomap types.
Signed-off-by: Shiyang Ruan
---
fs/dax.c | 291 +++
1 file changed, 145 insertions(+), 146 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 7031e4302b13..33ddad0f3091 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1053,6 +1053,66 @@ static vm_fault_t dax_load_hole(struct xa_state *xas,
return ret;
}
+#ifdef CONFIG_FS_DAX_PMD
+static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
+ struct iomap *iomap, void **entry)
+{
+ 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;
+ pfn_t pfn;
+
+ zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
+
+ if (unlikely(!zero_page))
+ goto fallback;
+
+ pfn = page_to_pfn_t(zero_page);
+ *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);
+ spin_unlock(ptl);
+ trace_dax_pmd_load_hole(inode, vmf, zero_page, *entry);
+ 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;
+}
+#else
+static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
+ struct iomap *iomap, void **entry)
+{
+ return VM_FAULT_FALLBACK;
+}
+#endif /* CONFIG_FS_DAX_PMD */
+
s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
{
sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
@@ -1289,6 +1349,61 @@ static int dax_fault_cow_page(struct vm_fault *vmf,
struct iomap *iomap,
return 0;
}
+/**
+ * dax_fault_actor - Common actor to handle pfn insertion in PTE/PMD fault.
+ * @vmf: vm fault instance
+ * @pfnp: pfn to be returned
+ * @xas: the dax mapping tree of a file
+ * @entry: an unlocked dax entry to be inserted
+ * @pmd: distinguish whether it is a pmd fault
+ * @flags: iomap flags
+ * @iomap: from iomap_begin()
+ * @srcmap:from iomap_begin(), not equal to iomap if it is a CoW
+ */
+static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp,
+ struct xa_state *xas, void *entry, bool pmd, unsigned int flags,
+ struct iomap *iomap, struct iomap *srcmap)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
+ loff_t pos = (loff_t)xas->xa_offset << PAGE_SHIFT;
shouldn't we use xa_index here for pos ?
(loff_t)xas->xa_index << PAGE_SHIFT;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+ bool sync = dax_fault_is_synchronous(flags, vmf->vma, iomap);
+ int err = 0;
+ pfn_t pfn;
+
+ /* if we are reading UNWRITTEN and HOLE, return a hole. */
+ if (!write &&
+ (iomap->type == IOMAP_UNWRITTEN || iomap->type == IOMAP_HOLE)) {
+ if (!pmd)
+ return dax_load_hole(xas, mapping, , vmf);
+ else
+ return dax_pmd_load_hole(xas, vmf, iomap, );
+ }
+
+ if (iomap->type != IOMAP_MAPPED) {
+ WARN_ON_ONCE(1);
+ return VM_FAULT_SIGBUS;
+ }
So now in case if mapping is not mapped, we always cause
VM_FAULT_SIGBUG. But earlier we were only doing WARN_ON_ONCE(1).
Can you pls help answer why the change in behavior?
+
+ err = dax_iomap_pfn(iomap, pos, size, );
+ if (err)
+ return dax_fault_return(err);
Same case here as well. This could return SIGBUS while earlier I am not
sure why were we only returning FALLBACK?
+
+ entry = dax_insert_entry(xas, mapping, vmf, entry, pfn, 0,
+
[PATCH v3 02/10] fsdax: Factor helper: dax_fault_actor()
The core logic in the two dax page fault functions is similar. So, move
the logic into a common helper function. Also, to facilitate the
addition of new features, such as CoW, switch-case is no longer used to
handle different iomap types.
Signed-off-by: Shiyang Ruan
---
fs/dax.c | 291 +++
1 file changed, 145 insertions(+), 146 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 7031e4302b13..33ddad0f3091 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1053,6 +1053,66 @@ static vm_fault_t dax_load_hole(struct xa_state *xas,
return ret;
}
+#ifdef CONFIG_FS_DAX_PMD
+static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
+ struct iomap *iomap, void **entry)
+{
+ 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;
+ pfn_t pfn;
+
+ zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
+
+ if (unlikely(!zero_page))
+ goto fallback;
+
+ pfn = page_to_pfn_t(zero_page);
+ *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);
+ spin_unlock(ptl);
+ trace_dax_pmd_load_hole(inode, vmf, zero_page, *entry);
+ 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;
+}
+#else
+static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
+ struct iomap *iomap, void **entry)
+{
+ return VM_FAULT_FALLBACK;
+}
+#endif /* CONFIG_FS_DAX_PMD */
+
s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
{
sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
@@ -1289,6 +1349,61 @@ static int dax_fault_cow_page(struct vm_fault *vmf,
struct iomap *iomap,
return 0;
}
+/**
+ * dax_fault_actor - Common actor to handle pfn insertion in PTE/PMD fault.
+ * @vmf: vm fault instance
+ * @pfnp: pfn to be returned
+ * @xas: the dax mapping tree of a file
+ * @entry: an unlocked dax entry to be inserted
+ * @pmd: distinguish whether it is a pmd fault
+ * @flags: iomap flags
+ * @iomap: from iomap_begin()
+ * @srcmap:from iomap_begin(), not equal to iomap if it is a CoW
+ */
+static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp,
+ struct xa_state *xas, void *entry, bool pmd, unsigned int flags,
+ struct iomap *iomap, struct iomap *srcmap)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
+ loff_t pos = (loff_t)xas->xa_offset << PAGE_SHIFT;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+ bool sync = dax_fault_is_synchronous(flags, vmf->vma, iomap);
+ int err = 0;
+ pfn_t pfn;
+
+ /* if we are reading UNWRITTEN and HOLE, return a hole. */
+ if (!write &&
+ (iomap->type == IOMAP_UNWRITTEN || iomap->type == IOMAP_HOLE)) {
+ if (!pmd)
+ return dax_load_hole(xas, mapping, , vmf);
+ else
+ return dax_pmd_load_hole(xas, vmf, iomap, );
+ }
+
+ if (iomap->type != IOMAP_MAPPED) {
+ WARN_ON_ONCE(1);
+ return VM_FAULT_SIGBUS;
+ }
+
+ err = dax_iomap_pfn(iomap, pos, size, );
+ if (err)
+ return dax_fault_return(err);
+
+ entry = dax_insert_entry(xas, mapping, vmf, entry, pfn, 0,
+write && !sync);
+
+ if (sync)
+ return dax_fault_synchronous_pfnp(pfnp, pfn);
+
+ if (pmd)
+ return vmf_insert_pfn_pmd(vmf, pfn, write);
+ if (write)
+ return vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
+ else
+ return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
+}
+
static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf,
