[v2,1/2] iomap: Add a page_prepare callback

Commit Message

Andreas Gruenbacher April 25, 2019, 3:26 p.m. UTC

Move the page_done callback into a separate iomap_page_ops structure and
add a page_prepare calback to be called before a page is written to.  In
gfs2, we'll want to start a transaction in page_prepare and end it in
page_done, and other filesystems that implement data journaling will
require the same kind of mechanism.

Signed-off-by: Andreas Gruenbacher <[e-mail]>
---
 fs/iomap.c            | 21 +++++++++++++++++----
 include/linux/iomap.h | 18 +++++++++++++-----
 2 files changed, 30 insertions(+), 9 deletions(-)

Comments

Matthew Wilcox (Oracle) April 25, 2019, 3:29 p.m. UTC | #1

On Thu, Apr 25, 2019 at 05:26:30PM +0200, Andreas Gruenbacher wrote:

This seems to be corrupted; there's no declaration of a page_ops in
iomap_write_begin ... unless you're basing on a patch I don't have?

> diff --git a/fs/iomap.c b/fs/iomap.c
> index 97cb9d486a7d..967c985c5310 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -674,9 +674,17 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
>  	if (fatal_signal_pending(current))
>  		return -EINTR;
>  
> +	if (page_ops) {
> +		status = page_ops->page_prepare(inode, pos, len, iomap);
> +		if (status)
> +			return status;
> +	}
> +
>  	page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
> -	if (!page)
> -		return -ENOMEM;
> +	if (!page) {
> +		status = -ENOMEM;
> +		goto no_page;
> +	}
>  
>  	if (iomap->type == IOMAP_INLINE)
>  		iomap_read_inline_data(inode, page, iomap);

Andreas Gruenbacher April 25, 2019, 3:52 p.m. UTC | #2

On Thu, 25 Apr 2019 at 17:29, Matthew Wilcox <[e-mail]> wrote:
>
> On Thu, Apr 25, 2019 at 05:26:30PM +0200, Andreas Gruenbacher wrote:
>
> This seems to be corrupted; there's no declaration of a page_ops in
> iomap_write_begin ... unless you're basing on a patch I don't have?

Oops, this has slipped into the 2nd patch, sorry.

> > diff --git a/fs/iomap.c b/fs/iomap.c
> > index 97cb9d486a7d..967c985c5310 100644
> > --- a/fs/iomap.c
> > +++ b/fs/iomap.c
> > @@ -674,9 +674,17 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> >       if (fatal_signal_pending(current))
> >               return -EINTR;
> >
> > +     if (page_ops) {
> > +             status = page_ops->page_prepare(inode, pos, len, iomap);
> > +             if (status)
> > +                     return status;
> > +     }
> > +
> >       page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
> > -     if (!page)
> > -             return -ENOMEM;
> > +     if (!page) {
> > +             status = -ENOMEM;
> > +             goto no_page;
> > +     }
> >
> >       if (iomap->type == IOMAP_INLINE)
> >               iomap_read_inline_data(inode, page, iomap);

Andreas

Patch

diff --git a/fs/iomap.c b/fs/iomap.c
index 97cb9d486a7d..967c985c5310 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -674,9 +674,17 @@  iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
 	if (fatal_signal_pending(current))
 		return -EINTR;
 
+	if (page_ops) {
+		status = page_ops->page_prepare(inode, pos, len, iomap);
+		if (status)
+			return status;
+	}
+
 	page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
-	if (!page)
-		return -ENOMEM;
+	if (!page) {
+		status = -ENOMEM;
+		goto no_page;
+	}
 
 	if (iomap->type == IOMAP_INLINE)
 		iomap_read_inline_data(inode, page, iomap);
@@ -684,12 +692,16 @@  iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
 		status = __block_write_begin_int(page, pos, len, NULL, iomap);
 	else
 		status = __iomap_write_begin(inode, pos, len, page, iomap);
+
 	if (unlikely(status)) {
 		unlock_page(page);
 		put_page(page);
 		page = NULL;
 
 		iomap_write_failed(inode, pos, len);
+no_page:
+		if (page_ops)
+			page_ops->page_done(inode, pos, 0, NULL, iomap);
 	}
 
 	*pagep = page;
@@ -769,6 +781,7 @@  static int
 iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
 		unsigned copied, struct page *page, struct iomap *iomap)
 {
+	const struct iomap_page_ops *page_ops = iomap->page_ops;
 	int ret;
 
 	if (iomap->type == IOMAP_INLINE) {
@@ -780,8 +793,8 @@  iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
 		ret = __iomap_write_end(inode, pos, len, copied, page, iomap);
 	}
 
-	if (iomap->page_done)
-		iomap->page_done(inode, pos, copied, page, iomap);
+	if (page_ops)
+		page_ops->page_done(inode, pos, copied, page, iomap);
 
 	if (ret < len)
 		iomap_write_failed(inode, pos, len);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 0fefb5455bda..fd65f27d300e 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -53,6 +53,8 @@  struct vm_fault;
  */
 #define IOMAP_NULL_ADDR -1ULL	/* addr is not valid */
 
+struct iomap_page_ops;
+
 struct iomap {
 	u64			addr; /* disk offset of mapping, bytes */
 	loff_t			offset;	/* file offset of mapping, bytes */
@@ -63,12 +65,18 @@  struct iomap {
 	struct dax_device	*dax_dev; /* dax_dev for dax operations */
 	void			*inline_data;
 	void			*private; /* filesystem private */
+	const struct iomap_page_ops *page_ops;
+};
 
-	/*
-	 * Called when finished processing a page in the mapping returned in
-	 * this iomap.  At least for now this is only supported in the buffered
-	 * write path.
-	 */
+/*
+ * Called before / after processing a page in the mapping returned in this
+ * iomap.  At least for now, this is only supported in the buffered write path.
+ * When page_prepare returns 0, page_done is called as well
+ * (possibly with page == NULL).
+ */
+struct iomap_page_ops {
+	int (*page_prepare)(struct inode *inode, loff_t pos, unsigned len,
+			struct iomap *iomap);
 	void (*page_done)(struct inode *inode, loff_t pos, unsigned copied,
 			struct page *page, struct iomap *iomap);
 };