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
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