2021-03-21 22:59:03

by Matthew Wilcox

Subject: [PATCH] btrfs: Use readahead_batch_length

Implement readahead_batch_length() to determine the number of bytes in
the current batch of readahead pages and use it in btrfs.

Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
---
fs/btrfs/extent_io.c | 6 ++----
include/linux/pagemap.h | 9 +++++++++
2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index e9837562f7d6..97ac4ddb2857 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4875,10 +4875,8 @@ void extent_readahead(struct readahead_control *rac)
int nr;

while ((nr = readahead_page_batch(rac, pagepool))) {
- u64 contig_start = page_offset(pagepool[0]);
- u64 contig_end = page_offset(pagepool[nr - 1]) + PAGE_SIZE - 1;
-
- ASSERT(contig_start + nr * PAGE_SIZE - 1 == contig_end);
+ u64 contig_start = readahead_pos(rac);
+ u64 contig_end = contig_start + readahead_batch_length(rac) - 1;

contiguous_readpages(pagepool, nr, contig_start, contig_end,
&em_cached, &bio, &bio_flags, &prev_em_start);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 2cbfd4c36026..92939afd4944 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1174,6 +1174,15 @@ static inline unsigned int readahead_count(struct readahead_control *rac)
return rac->_nr_pages;
}

+/**
+ * readahead_batch_length - The number of bytes in the current batch.
+ * @rac: The readahead request.
+ */
+static inline loff_t readahead_batch_length(struct readahead_control *rac)
+{
+ return rac->_batch_count * PAGE_SIZE;
+}
+
static inline unsigned long dir_pages(struct inode *inode)
{
return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
--
2.30.2

2021-03-30 17:42:59

by Matthew Wilcox

Subject: Re: [PATCH] btrfs: Use readahead_batch_length

ping?

On Sun, Mar 21, 2021 at 09:03:11PM +0000, Matthew Wilcox (Oracle) wrote:
> Implement readahead_batch_length() to determine the number of bytes in
> the current batch of readahead pages and use it in btrfs.
>
> Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
> ---
> fs/btrfs/extent_io.c | 6 ++----
> include/linux/pagemap.h | 9 +++++++++
> 2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index e9837562f7d6..97ac4ddb2857 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4875,10 +4875,8 @@ void extent_readahead(struct readahead_control *rac)
> int nr;
>
> while ((nr = readahead_page_batch(rac, pagepool))) {
> - u64 contig_start = page_offset(pagepool[0]);
> - u64 contig_end = page_offset(pagepool[nr - 1]) + PAGE_SIZE - 1;
> -
> - ASSERT(contig_start + nr * PAGE_SIZE - 1 == contig_end);
> + u64 contig_start = readahead_pos(rac);
> + u64 contig_end = contig_start + readahead_batch_length(rac) - 1;
>
> contiguous_readpages(pagepool, nr, contig_start, contig_end,
> &em_cached, &bio, &bio_flags, &prev_em_start);
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 2cbfd4c36026..92939afd4944 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -1174,6 +1174,15 @@ static inline unsigned int readahead_count(struct readahead_control *rac)
> return rac->_nr_pages;
> }
>
> +/**
> + * readahead_batch_length - The number of bytes in the current batch.
> + * @rac: The readahead request.
> + */
> +static inline loff_t readahead_batch_length(struct readahead_control *rac)
> +{
> + return rac->_batch_count * PAGE_SIZE;
> +}
> +
> static inline unsigned long dir_pages(struct inode *inode)
> {
> return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
> --
> 2.30.2
>

2021-04-07 08:25:00

by David Sterba

Subject: Re: [PATCH] btrfs: Use readahead_batch_length

On Sun, Mar 21, 2021 at 09:03:11PM +0000, Matthew Wilcox (Oracle) wrote:
> Implement readahead_batch_length() to determine the number of bytes in
> the current batch of readahead pages and use it in btrfs.
>
> Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>

Thanks, I'll take it through my tree as btrfs is probably the only user
of the new helper. The MM list hasn't been CCed, I've added it now but I
think the patch is trivial enough and does not need another ack, so it's
just for the record.

> ---
> fs/btrfs/extent_io.c | 6 ++----
> include/linux/pagemap.h | 9 +++++++++
> 2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index e9837562f7d6..97ac4ddb2857 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4875,10 +4875,8 @@ void extent_readahead(struct readahead_control *rac)
> int nr;
>
> while ((nr = readahead_page_batch(rac, pagepool))) {
> - u64 contig_start = page_offset(pagepool[0]);
> - u64 contig_end = page_offset(pagepool[nr - 1]) + PAGE_SIZE - 1;
> -
> - ASSERT(contig_start + nr * PAGE_SIZE - 1 == contig_end);
> + u64 contig_start = readahead_pos(rac);
> + u64 contig_end = contig_start + readahead_batch_length(rac) - 1;
>
> contiguous_readpages(pagepool, nr, contig_start, contig_end,
> &em_cached, &bio, &bio_flags, &prev_em_start);
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 2cbfd4c36026..92939afd4944 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -1174,6 +1174,15 @@ static inline unsigned int readahead_count(struct readahead_control *rac)
> return rac->_nr_pages;
> }
>
> +/**
> + * readahead_batch_length - The number of bytes in the current batch.
> + * @rac: The readahead request.
> + */
> +static inline loff_t readahead_batch_length(struct readahead_control *rac)
> +{
> + return rac->_batch_count * PAGE_SIZE;
> +}
> +
> static inline unsigned long dir_pages(struct inode *inode)
> {
> return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>

--