[RFC PATCH 3/6] mm: Push readahead_control down into force_page_cache_readahead() [ver #2]

[David Howells]

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 <dhowe...@redhat.com>
---

 mm/fadvise.c   |    5 ++++-
 mm/internal.h  |    3 +--
 mm/readahead.c |   19 +++++++++++--------
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/mm/fadvise.c b/mm/fadvise.c
index 0e66f2aaeea3..997f7c16690a 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -104,7 +104,10 @@ 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);
+                       force_page_cache_readahead(&rac, nrpages);
+               }
                break;
        case POSIX_FADV_NOREUSE:
                break;
diff --git a/mm/internal.h b/mm/internal.h
index bf2bee6c42a1..c8ccf208f524 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 *, unsigned long);
 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 e3e3419dfe3d..366357e6e845 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -271,13 +271,13 @@ 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,
+               unsigned long nr_to_read)
 {
-       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;
 
        if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages &&
                        !mapping->a_ops->readahead))
@@ -287,14 +287,17 @@ 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, nr_to_read, 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;
+               __do_page_cache_readahead(rac, this_chunk, 0);
 
                index += this_chunk;
                nr_to_read -= this_chunk;
@@ -656,7 +659,7 @@ 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, req_count);
                return;
        }