From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: Re: [PATCH 10/18] dax: replace mmap entry in case of CoW Date: Wed, 17 Apr 2019 08:24:53 -0700 Message-ID: <20190417152453.GA4740@magnolia> References: <20190416164154.30390-1-rgoldwyn@suse.de> <20190416164154.30390-11-rgoldwyn@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20190416164154.30390-11-rgoldwyn-l3A5Bk7waGM@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Goldwyn Rodrigues Cc: kilobyte-b9QjgO8OEXPVItvQsEIGlw@public.gmane.org, jack-AlSwsSmVLrQ@public.gmane.org, linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, nborisov-IBi9RG/b67k@public.gmane.org, david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org, dsterba-AlSwsSmVLrQ@public.gmane.org, willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, Goldwyn Rodrigues , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, hch-jcswGhMUV9g@public.gmane.org, linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-nvdimm@lists.01.org On Tue, Apr 16, 2019 at 11:41:46AM -0500, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > We replace the existing entry to the newly allocated one > in case of CoW. Also, we mark the entry as PAGECACHE_TAG_TOWRITE > so writeback marks this entry as writeprotected. This > helps us snapshots so new write pagefaults after snapshots > trigger a CoW. > > Signed-off-by: Goldwyn Rodrigues > --- > fs/dax.c | 23 +++++++++++++++-------- > 1 file changed, 15 insertions(+), 8 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index 45fc2e18969a..d5100cbe8bd2 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -708,14 +708,15 @@ static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev, > */ > static void *dax_insert_entry(struct xa_state *xas, > struct address_space *mapping, struct vm_fault *vmf, > - void *entry, pfn_t pfn, unsigned long flags, bool dirty) > + void *entry, pfn_t pfn, unsigned long flags, bool dirty, > + bool cow) I still wish these were flags instead of double booleans that will be easy to mix up, especially since this is a static function and nobody else has to see the flags... #define IE_DIRTY (1 << 0) /* mark entry and inode dirty */ #define IE_REPLACE (1 << 1) /* replacing one page with another */ ...otoh maybe I'll just defer to the maintainer. :) > { > void *new_entry = dax_make_entry(pfn, flags); > > if (dirty) > __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); > > - if (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE)) { > + if (cow || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) { > unsigned long index = xas->xa_index; > /* we are replacing a zero page with block mapping */ These comments need updating. Otherwise looks good to me... --D > if (dax_is_pmd_entry(entry)) > @@ -727,12 +728,12 @@ static void *dax_insert_entry(struct xa_state *xas, > > xas_reset(xas); > xas_lock_irq(xas); > - if (dax_entry_size(entry) != dax_entry_size(new_entry)) { > + if (cow || (dax_entry_size(entry) != dax_entry_size(new_entry))) { > dax_disassociate_entry(entry, mapping, false); > dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address); > } > > - if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { > + if (cow || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { > /* > * Only swap our new entry into the page cache if the current > * entry is a zero page or an empty entry. If a normal PTE or > @@ -752,6 +753,9 @@ static void *dax_insert_entry(struct xa_state *xas, > if (dirty) > xas_set_mark(xas, PAGECACHE_TAG_DIRTY); > > + if (cow) > + xas_set_mark(xas, PAGECACHE_TAG_TOWRITE); > + > xas_unlock_irq(xas); > return entry; > } > @@ -1031,7 +1035,7 @@ static vm_fault_t dax_load_hole(struct xa_state *xas, > vm_fault_t ret; > > *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, > - DAX_ZERO_PAGE, false); > + DAX_ZERO_PAGE, false, false); > > ret = vmf_insert_mixed(vmf->vma, vaddr, pfn); > trace_dax_load_hole(inode, vmf, ret); > @@ -1388,7 +1392,8 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, > memset(addr, 0, PAGE_SIZE); > } > entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn, > - 0, write && !sync); > + 0, write && !sync, > + iomap.type == IOMAP_DAX_COW); > > /* > * If we are doing synchronous page fault and inode needs fsync, > @@ -1467,7 +1472,8 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, > > pfn = page_to_pfn_t(zero_page); > *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, > - DAX_PMD | DAX_ZERO_PAGE, false); > + DAX_PMD | DAX_ZERO_PAGE, false, > + iomap->type == IOMAP_DAX_COW); > > ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); > if (!pmd_none(*(vmf->pmd))) { > @@ -1590,7 +1596,8 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, > goto finish_iomap; > > entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn, > - DAX_PMD, write && !sync); > + DAX_PMD, write && !sync, > + false); > > /* > * If we are doing synchronous page fault and inode needs fsync, > -- > 2.16.4 >