From: Goldwyn Rodrigues <rgold...@suse.com> 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 <rgold...@suse.com> --- 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) { 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 */ 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 _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm