[RFC PATCH 3/7] mm: Push readahead_control down into force_page_cache_readahead()

David Howells
2020-09-01T16:28:52Z

Push readahead_control down into force_page_cache_readahead() from its
callers in preparation for making do_sync_mmap_readahead() pass down an RAC
struct.

Signed-off-by: David Howells <dhowells@redhat.com>
---

mm/fadvise.c | 6 +++++-
mm/internal.h | 3 +--
mm/readahead.c | 20 ++++++++++++--------
3 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/mm/fadvise.c b/mm/fadvise.c
index 0e66f2aaeea3..b68d2f2959d5 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -104,7 +104,11 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
if (!nrpages)
nrpages = ~0UL;

- force_page_cache_readahead(mapping, file, start_index, nrpages);
+ {
+ DEFINE_READAHEAD(rac, file, mapping, start_index);
+ rac._nr_pages = nrpages;
+ force_page_cache_readahead(&rac);
+ }
break;
case POSIX_FADV_NOREUSE:
break;
diff --git a/mm/internal.h b/mm/internal.h
index bf2bee6c42a1..2eb9f7f5f134 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -49,8 +49,7 @@ void unmap_page_range(struct mmu_gather *tlb,
unsigned long addr, unsigned long end,
struct zap_details *details);

-void force_page_cache_readahead(struct address_space *, struct file *,
- pgoff_t index, unsigned long nr_to_read);
+void force_page_cache_readahead(struct readahead_control *);
void __do_page_cache_readahead(struct readahead_control *,
unsigned long nr_to_read, unsigned long lookahead_size);

diff --git a/mm/readahead.c b/mm/readahead.c
index 0e16fb4809f5..e557c6d5a183 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -271,13 +271,12 @@ void __do_page_cache_readahead(struct readahead_control *rac,
* Chunk the readahead into 2 megabyte units, so that we don't pin too much
* memory at once.
*/
-void force_page_cache_readahead(struct address_space *mapping,
- struct file *file, pgoff_t index, unsigned long nr_to_read)
+void force_page_cache_readahead(struct readahead_control *rac)
{
- DEFINE_READAHEAD(rac, file, mapping, index);
+ struct address_space *mapping = rac->mapping;
struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
- struct file_ra_state *ra = &file->f_ra;
- unsigned long max_pages;
+ struct file_ra_state *ra = &rac->file->f_ra;
+ unsigned long max_pages, index, nr_to_read;

if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages &&
!mapping->a_ops->readahead))
@@ -287,14 +286,19 @@ void force_page_cache_readahead(struct address_space *mapping,
* If the request exceeds the readahead window, allow the read to
* be up to the optimal hardware IO size
*/
+ index = readahead_index(rac);
max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages);
- nr_to_read = min(nr_to_read, max_pages);
+ nr_to_read = min_t(unsigned long, readahead_count(rac), max_pages);
while (nr_to_read) {
unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE;

if (this_chunk > nr_to_read)
this_chunk = nr_to_read;
- __do_page_cache_readahead(&rac, this_chunk, 0);
+
+ rac->_index = index;
+ rac->_nr_pages = this_chunk;
+ // Do I need to modify rac->_batch_count?
+ __do_page_cache_readahead(rac, this_chunk, 0);

index += this_chunk;
nr_to_read -= this_chunk;
@@ -658,7 +662,7 @@ void page_cache_sync_readahead(struct address_space *mapping,

/* be dumb */
if (filp && (filp->f_mode & FMODE_RANDOM)) {
- force_page_cache_readahead(mapping, filp, index, req_count);
+ force_page_cache_readahead(&rac);
return;
}