[08/18] dax: memcpy page in case of IOMAP_DAX_COW for mmap faults
diff mbox series

Message ID 20190416164154.30390-9-rgoldwyn@suse.de
State New
Headers show
Series
  • btrfs dax support
Related show

Commit Message

Goldwyn Rodrigues April 16, 2019, 4:41 p.m. UTC
From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Change dax_iomap_pfn to return the address as well in order to
use it for performing a memcpy in case the type is IOMAP_DAX_COW.

Question:
The sequence of bdev_dax_pgoff() and dax_direct_access() is
used multiple times to calculate address and pfn's. Would it make
sense to call it while calculating address as well to reduce code?

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/dax.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Comments

Darrick J. Wong April 17, 2019, 4:52 p.m. UTC | #1
On Tue, Apr 16, 2019 at 11:41:44AM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> Change dax_iomap_pfn to return the address as well in order to
> use it for performing a memcpy in case the type is IOMAP_DAX_COW.
> 
> Question:
> The sequence of bdev_dax_pgoff() and dax_direct_access() is
> used multiple times to calculate address and pfn's. Would it make
> sense to call it while calculating address as well to reduce code?
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  fs/dax.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 4b4ac51fbd16..45fc2e18969a 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -983,7 +983,7 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
>  }
>  
>  static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
> -			 pfn_t *pfnp)
> +			 pfn_t *pfnp, void **addr)
>  {
>  	const sector_t sector = dax_iomap_sector(iomap, pos);
>  	pgoff_t pgoff;
> @@ -995,7 +995,7 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
>  		return rc;
>  	id = dax_read_lock();
>  	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
> -				   NULL, pfnp);
> +				   addr, pfnp);
>  	if (length < 0) {
>  		rc = length;
>  		goto out;
> @@ -1280,6 +1280,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
>  	XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
>  	struct inode *inode = mapping->host;
>  	unsigned long vaddr = vmf->address;
> +	void *addr;
>  	loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
>  	struct iomap iomap = { 0 };
>  	unsigned flags = IOMAP_FAULT;
> @@ -1369,16 +1370,23 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
>  	sync = dax_fault_is_synchronous(flags, vma, &iomap);
>  
>  	switch (iomap.type) {
> +	case IOMAP_DAX_COW:
>  	case IOMAP_MAPPED:
>  		if (iomap.flags & IOMAP_F_NEW) {
>  			count_vm_event(PGMAJFAULT);
>  			count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
>  			major = VM_FAULT_MAJOR;
>  		}
> -		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
> +		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn, &addr);
>  		if (error < 0)
>  			goto error_finish_iomap;
>  
> +		if (iomap.type == IOMAP_DAX_COW) {
> +			if (iomap.inline_data)
> +				memcpy(addr, iomap.inline_data, PAGE_SIZE);

Same memcpy_mcsafe question from my reply to patch 4 applies here.

> +			else
> +				memset(addr, 0, PAGE_SIZE);
> +		}
>  		entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn,
>  						 0, write && !sync);
>  
> @@ -1577,7 +1585,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
>  
>  	switch (iomap.type) {
>  	case IOMAP_MAPPED:
> -		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
> +		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn, NULL);

Same (unanswered) question from the v2 series -- doesn't a PMD fault
also require handling IOMAP_DAX_COW?

--D

>  		if (error < 0)
>  			goto finish_iomap;
>  
> -- 
> 2.16.4
>

Patch
diff mbox series

diff --git a/fs/dax.c b/fs/dax.c
index 4b4ac51fbd16..45fc2e18969a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -983,7 +983,7 @@  static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
 }
 
 static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
-			 pfn_t *pfnp)
+			 pfn_t *pfnp, void **addr)
 {
 	const sector_t sector = dax_iomap_sector(iomap, pos);
 	pgoff_t pgoff;
@@ -995,7 +995,7 @@  static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
 		return rc;
 	id = dax_read_lock();
 	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
-				   NULL, pfnp);
+				   addr, pfnp);
 	if (length < 0) {
 		rc = length;
 		goto out;
@@ -1280,6 +1280,7 @@  static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
 	struct inode *inode = mapping->host;
 	unsigned long vaddr = vmf->address;
+	void *addr;
 	loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
 	struct iomap iomap = { 0 };
 	unsigned flags = IOMAP_FAULT;
@@ -1369,16 +1370,23 @@  static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	sync = dax_fault_is_synchronous(flags, vma, &iomap);
 
 	switch (iomap.type) {
+	case IOMAP_DAX_COW:
 	case IOMAP_MAPPED:
 		if (iomap.flags & IOMAP_F_NEW) {
 			count_vm_event(PGMAJFAULT);
 			count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
 			major = VM_FAULT_MAJOR;
 		}
-		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
+		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn, &addr);
 		if (error < 0)
 			goto error_finish_iomap;
 
+		if (iomap.type == IOMAP_DAX_COW) {
+			if (iomap.inline_data)
+				memcpy(addr, iomap.inline_data, PAGE_SIZE);
+			else
+				memset(addr, 0, PAGE_SIZE);
+		}
 		entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn,
 						 0, write && !sync);
 
@@ -1577,7 +1585,7 @@  static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 
 	switch (iomap.type) {
 	case IOMAP_MAPPED:
-		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
+		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn, NULL);
 		if (error < 0)
 			goto finish_iomap;