2023-09-16 02:21:18

by Pankaj Raghav (Samsung)

Subject: [RFC 02/23] pagemap: use mapping_min_order in fgf_set_order()

From: Pankaj Raghav <[email protected]>

fgf_set_order() encodes optimal order in fgp flags. Set it to at least
mapping_min_order from the page cache. Default to the old behaviour if
min_order is not set.

Signed-off-by: Pankaj Raghav <[email protected]>
---
fs/iomap/buffered-io.c | 2 +-
include/linux/pagemap.h | 9 +++++----
2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index ae8673ce08b1..d4613fd550c4 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -549,7 +549,7 @@ struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len)

if (iter->flags & IOMAP_NOWAIT)
fgp |= FGP_NOWAIT;
- fgp |= fgf_set_order(len);
+ fgp |= fgf_set_order(iter->inode->i_mapping, len);

return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
fgp, mapping_gfp_mask(iter->inode->i_mapping));
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index d2b5308cc59e..5d392366420a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -620,6 +620,7 @@ typedef unsigned int __bitwise fgf_t;

/**
* fgf_set_order - Encode a length in the fgf_t flags.
+ * @mapping: address_space struct from the inode
* @size: The suggested size of the folio to create.
*
* The caller of __filemap_get_folio() can use this to suggest a preferred
@@ -629,13 +630,13 @@ typedef unsigned int __bitwise fgf_t;
* due to alignment constraints, memory pressure, or the presence of
* other folios at nearby indices.
*/
-static inline fgf_t fgf_set_order(size_t size)
+static inline fgf_t fgf_set_order(struct address_space *mapping, size_t size)
{
unsigned int shift = ilog2(size);
+ unsigned int min_order = mapping_min_folio_order(mapping);
+ int order = max(min_order, shift - PAGE_SHIFT);

- if (shift <= PAGE_SHIFT)
- return 0;
- return (__force fgf_t)((shift - PAGE_SHIFT) << 26);
+ return (__force fgf_t)((order) << 26);
}

void *filemap_get_entry(struct address_space *mapping, pgoff_t index);
--
2.40.1

2023-09-16 10:56:54

by Matthew Wilcox

Subject: Re: [RFC 02/23] pagemap: use mapping_min_order in fgf_set_order()

On Fri, Sep 15, 2023 at 08:38:27PM +0200, Pankaj Raghav wrote:
> From: Pankaj Raghav <[email protected]>
>
> fgf_set_order() encodes optimal order in fgp flags. Set it to at least
> mapping_min_order from the page cache. Default to the old behaviour if
> min_order is not set.

Why not simply:

+++ b/mm/filemap.c
@@ -1906,9 +1906,12 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
folio_wait_stable(folio);
no_page:
if (!folio && (fgp_flags & FGP_CREAT)) {
- unsigned order = FGF_GET_ORDER(fgp_flags);
+ unsigned order;
int err;

+ order = min(mapping_min_folio_order(mapping),
+ FGF_GET_ORDER(fgp_flags));

2023-09-20 09:49:21

by Pankaj Raghav

Subject: Re: [RFC 02/23] pagemap: use mapping_min_order in fgf_set_order()

On 2023-09-15 20:55, Matthew Wilcox wrote:
> On Fri, Sep 15, 2023 at 08:38:27PM +0200, Pankaj Raghav wrote:
>> From: Pankaj Raghav <[email protected]>
>>
>> fgf_set_order() encodes optimal order in fgp flags. Set it to at least
>> mapping_min_order from the page cache. Default to the old behaviour if
>> min_order is not set.
>
> Why not simply:
>

That is a good idea to move this to filemap instead of changing it in iomap. I will do that!

> +++ b/mm/filemap.c
> @@ -1906,9 +1906,12 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> folio_wait_stable(folio);
> no_page:
> if (!folio && (fgp_flags & FGP_CREAT)) {
> - unsigned order = FGF_GET_ORDER(fgp_flags);
> + unsigned order;
> int err;
>
> + order = min(mapping_min_folio_order(mapping),
> + FGF_GET_ORDER(fgp_flags));
>

I think this needs to max(mapping..., FGF...)