Messages in this thread | | | Date | Wed, 3 Mar 2021 10:28:08 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH v2 02/10] fsdax: Factor helper: dax_fault_actor() |
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On Fri, Feb 26, 2021 at 08:20:22AM +0800, 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 <ruansy.fnst@fujitsu.com> > --- > fs/dax.c | 211 ++++++++++++++++++++++++++++++------------------------- > 1 file changed, 117 insertions(+), 94 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index 7031e4302b13..9dea1572868e 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -1289,6 +1289,93 @@ static int dax_fault_cow_page(struct vm_fault *vmf, struct iomap *iomap, > return 0; > } > > +static vm_fault_t dax_fault_insert_pfn(struct vm_fault *vmf, pfn_t pfn, > + bool pmd, bool write) > +{ > + vm_fault_t ret; > + > + if (!pmd) { > + struct vm_area_struct *vma = vmf->vma; > + unsigned long address = vmf->address; > + > + if (write) > + ret = vmf_insert_mixed_mkwrite(vma, address, pfn); > + else > + ret = vmf_insert_mixed(vma, address, pfn); > + } else > + ret = vmf_insert_pfn_pmd(vmf, pfn, write);
What about simplifying this a little bit more, something like:
if (pmd) return vmf_insert_pfn_pmd(vmf, pfn, write);
if (write) return vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn); return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
also given that this only has a single user, why not keep open coding it in the caller?
> +#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); > +#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
Can we try to avoid the forward declaration? Also is there a reason dax_pmd_load_hole does not compile for the !CONFIG_FS_DAX_PMD case? If it compiles fine we can just rely on IS_ENABLED() based dead code elimination entirely.
> + /* 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, &entry, vmf); > + else > + return dax_pmd_load_hole(xas, vmf, iomap, &entry); > + } > + > + if (iomap->type != IOMAP_MAPPED) { > + WARN_ON_ONCE(1); > + return VM_FAULT_SIGBUS; > + }
Nit: I'd use a switch statement here for a clarity:
switch (iomap->type) { case IOMAP_MAPPED: break; case IOMAP_UNWRITTEN: case IOMAP_HOLE: if (!write) { if (!pmd) return dax_load_hole(xas, mapping, &entry, vmf); return dax_pmd_load_hole(xas, vmf, iomap, &entry); } break; default: WARN_ON_ONCE(1); return VM_FAULT_SIGBUS; }
> + err = dax_iomap_pfn(iomap, pos, size, &pfn); > + if (err) > + goto error_fault; > + > + entry = dax_insert_entry(xas, mapping, vmf, entry, pfn, 0, > + write && !sync); > + > + if (sync) > + return dax_fault_synchronous_pfnp(pfnp, pfn); > + > + ret = dax_fault_insert_pfn(vmf, pfn, pmd, write); > + > +error_fault: > + if (err) > + ret = dax_fault_return(err); > + > + return ret;
It seems like the only place that sets err is the dax_iomap_pfn case above. So I'd move the dax_fault_return there, which then allows a direct return for everyone else, including the open coded version of dax_fault_insert_pfn.
I really like where this is going!
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