Re: [PATCH 17/27] iomap: switch iomap_seek_hole to use iomap_iter

[Darrick J. Wong]

On Mon, Jul 26, 2021 at 10:22:36AM +0200, Christoph Hellwig wrote:
> On Mon, Jul 19, 2021 at 10:22:47AM -0700, Darrick J. Wong wrote:
> > > -static loff_t
> > > -iomap_seek_hole_actor(struct inode *inode, loff_t start, loff_t length,
> > > -   void *data, struct iomap *iomap, struct iomap *srcmap)
> > > +static loff_t iomap_seek_hole_iter(const struct iomap_iter *iter, loff_t 
> > > *pos)
> > 
> > /me wonders if @pos should be named hole_pos (here and in the caller) to
> > make it a little easier to read...
> 
> Sure.
> 
> > ...because what we're really saying here is that if seek_hole_iter found
> > a hole (and returned zero, thereby terminating the loop before iter.len
> > could reach zero), we want to return the position of the hole.
> 
> Yes.
> 
> > > + return size;
> > 
> > Not sure why we return size here...?  Oh, because there's an implicit
> > hole at EOF, so we return i_size.  Uh, does this do the right thing if
> > ->iomap_begin returns posteof mappings?  I don't see anything in
> > iomap_iter_advance that would stop iteration at EOF.
> 
> Nothing in ->iomap_begin checks that, iomap_seek_hole initializes
> iter.len so that it stops at EOF.

Oh, right.  Sorry, I forgot that. :(

--D

Re: [PATCH 17/27] iomap: switch iomap_seek_hole to use iomap_iter

[Darrick J. Wong]

On Mon, Jul 19, 2021 at 12:35:10PM +0200, Christoph Hellwig wrote:
> Rewrite iomap_seek_hole to use iomap_iter.
> 
> Signed-off-by: Christoph Hellwig 
> ---
>  fs/iomap/seek.c | 46 +++---
>  1 file changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
> index ce6fb810854fec..7d6ed9af925e96 100644
> --- a/fs/iomap/seek.c
> +++ b/fs/iomap/seek.c
> @@ -1,7 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
>   * Copyright (C) 2017 Red Hat, Inc.
> - * Copyright (c) 2018 Christoph Hellwig.
> + * Copyright (c) 2018-2021 Christoph Hellwig.
>   */
>  #include 
>  #include 
> @@ -10,21 +10,19 @@
>  #include 
>  #include 
>  
> -static loff_t
> -iomap_seek_hole_actor(struct inode *inode, loff_t start, loff_t length,
> -   void *data, struct iomap *iomap, struct iomap *srcmap)
> +static loff_t iomap_seek_hole_iter(const struct iomap_iter *iter, loff_t 
> *pos)

/me wonders if @pos should be named hole_pos (here and in the caller) to
make it a little easier to read...

>  {
> - loff_t offset = start;
> + loff_t length = iomap_length(iter);
>  
> - switch (iomap->type) {
> + switch (iter->iomap.type) {
>   case IOMAP_UNWRITTEN:
> - offset = mapping_seek_hole_data(inode->i_mapping, start,
> - start + length, SEEK_HOLE);
> - if (offset == start + length)
> + *pos = mapping_seek_hole_data(iter->inode->i_mapping,
> + iter->pos, iter->pos + length, SEEK_HOLE);
> + if (*pos == iter->pos + length)
>   return length;
> - fallthrough;
> + return 0;
>   case IOMAP_HOLE:
> - *(loff_t *)data = offset;
> + *pos = iter->pos;
>   return 0;
>   default:
>   return length;
> @@ -35,23 +33,25 @@ loff_t
>  iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops 
> *ops)
>  {
>   loff_t size = i_size_read(inode);
> - loff_t ret;
> + struct iomap_iter iter = {
> + .inode  = inode,
> + .pos= offset,
> + .flags  = IOMAP_REPORT,
> + };
> + int ret;
>  
>   /* Nothing to be found before or beyond the end of the file. */
>   if (offset < 0 || offset >= size)
>   return -ENXIO;
>  
> - while (offset < size) {
> - ret = iomap_apply(inode, offset, size - offset, IOMAP_REPORT,
> -   ops, , iomap_seek_hole_actor);
> - if (ret < 0)
> - return ret;
> - if (ret == 0)
> - break;
> - offset += ret;
> - }
> -
> - return offset;
> + iter.len = size - offset;
> + while ((ret = iomap_iter(, ops)) > 0)
> + iter.processed = iomap_seek_hole_iter(, );
> + if (ret < 0)
> + return ret;
> + if (iter.len)
> + return offset;

...because what we're really saying here is that if seek_hole_iter found
a hole (and returned zero, thereby terminating the loop before iter.len
could reach zero), we want to return the position of the hole.

> + return size;

Not sure why we return size here...?  Oh, because there's an implicit
hole at EOF, so we return i_size.  Uh, does this do the right thing if
->iomap_begin returns posteof mappings?  I don't see anything in
iomap_iter_advance that would stop iteration at EOF.

--D

>  }
>  EXPORT_SYMBOL_GPL(iomap_seek_hole);
>  
> -- 
> 2.30.2
> 

[PATCH 17/27] iomap: switch iomap_seek_hole to use iomap_iter

[Christoph Hellwig]

Rewrite iomap_seek_hole to use iomap_iter.

Signed-off-by: Christoph Hellwig 
---
 fs/iomap/seek.c | 46 +++---
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
index ce6fb810854fec..7d6ed9af925e96 100644
--- a/fs/iomap/seek.c
+++ b/fs/iomap/seek.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2017 Red Hat, Inc.
- * Copyright (c) 2018 Christoph Hellwig.
+ * Copyright (c) 2018-2021 Christoph Hellwig.
  */
 #include 
 #include 
@@ -10,21 +10,19 @@
 #include 
 #include 
 
-static loff_t
-iomap_seek_hole_actor(struct inode *inode, loff_t start, loff_t length,
- void *data, struct iomap *iomap, struct iomap *srcmap)
+static loff_t iomap_seek_hole_iter(const struct iomap_iter *iter, loff_t *pos)
 {
-   loff_t offset = start;
+   loff_t length = iomap_length(iter);
 
-   switch (iomap->type) {
+   switch (iter->iomap.type) {
case IOMAP_UNWRITTEN:
-   offset = mapping_seek_hole_data(inode->i_mapping, start,
-   start + length, SEEK_HOLE);
-   if (offset == start + length)
+   *pos = mapping_seek_hole_data(iter->inode->i_mapping,
+   iter->pos, iter->pos + length, SEEK_HOLE);
+   if (*pos == iter->pos + length)
return length;
-   fallthrough;
+   return 0;
case IOMAP_HOLE:
-   *(loff_t *)data = offset;
+   *pos = iter->pos;
return 0;
default:
return length;
@@ -35,23 +33,25 @@ loff_t
 iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops 
*ops)
 {
loff_t size = i_size_read(inode);
-   loff_t ret;
+   struct iomap_iter iter = {
+   .inode  = inode,
+   .pos= offset,
+   .flags  = IOMAP_REPORT,
+   };
+   int ret;
 
/* Nothing to be found before or beyond the end of the file. */
if (offset < 0 || offset >= size)
return -ENXIO;
 
-   while (offset < size) {
-   ret = iomap_apply(inode, offset, size - offset, IOMAP_REPORT,
- ops, , iomap_seek_hole_actor);
-   if (ret < 0)
-   return ret;
-   if (ret == 0)
-   break;
-   offset += ret;
-   }
-
-   return offset;
+   iter.len = size - offset;
+   while ((ret = iomap_iter(, ops)) > 0)
+   iter.processed = iomap_seek_hole_iter(, );
+   if (ret < 0)
+   return ret;
+   if (iter.len)
+   return offset;
+   return size;
 }
 EXPORT_SYMBOL_GPL(iomap_seek_hole);
 
-- 
2.30.2