mm: return void from various readahead functions

ondemand_readahead has two callers, neither of which use the return
value.  That means that both ra_submit and __do_page_cache_readahead()
can return void, and we don't need to worry that a present page in the
readahead window causes us to return a smaller nr_pages than we ought to
have.

Similarly, no caller uses the return value from
force_page_cache_readahead().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Gao Xiang <gaoxiang25@huawei.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-3-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/fadvise.c b/mm/fadvise.c
index 3efebfb..0e66f2a 100644 (file)
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -104,10 +104,6 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
                if (!nrpages)
                        nrpages = ~0UL;
 
-               /*
-                * Ignore return value because fadvise() shall return
-                * success even if filesystem can't retrieve a hint,
-                */
                force_page_cache_readahead(mapping, file, start_index, nrpages);
                break;
        case POSIX_FADV_NOREUSE:

diff --git a/mm/internal.h b/mm/internal.h
index 25fee17..f762a34 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -49,20 +49,20 @@ void unmap_page_range(struct mmu_gather *tlb,
                             unsigned long addr, unsigned long end,
                             struct zap_details *details);
 
-int force_page_cache_readahead(struct address_space *, struct file *,
+void force_page_cache_readahead(struct address_space *, struct file *,
                pgoff_t index, unsigned long nr_to_read);
-extern unsigned int __do_page_cache_readahead(struct address_space *mapping,
-               struct file *filp, pgoff_t offset, unsigned long nr_to_read,
+void __do_page_cache_readahead(struct address_space *, struct file *,
+               pgoff_t index, unsigned long nr_to_read,
                unsigned long lookahead_size);
 
 /*
  * Submit IO for the read-ahead request in file_ra_state.
  */
-static inline unsigned long ra_submit(struct file_ra_state *ra,
+static inline void ra_submit(struct file_ra_state *ra,
                struct address_space *mapping, struct file *filp)
 {
-       return __do_page_cache_readahead(mapping, filp,
-                                       ra->start, ra->size, ra->async_size);
+       __do_page_cache_readahead(mapping, filp,
+                       ra->start, ra->size, ra->async_size);
 }
 
 /**

diff --git a/mm/readahead.c b/mm/readahead.c
index 2fe72cd..41a5928 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -149,10 +149,8 @@ out:
  * the pages first, then submits them for I/O. This avoids the very bad
  * behaviour which would occur if page allocations are causing VM writeback.
  * We really don't want to intermingle reads and writes like that.
- *
- * Returns the number of pages requested, or the maximum amount of I/O allowed.
  */
-unsigned int __do_page_cache_readahead(struct address_space *mapping,
+void __do_page_cache_readahead(struct address_space *mapping,
                struct file *filp, pgoff_t offset, unsigned long nr_to_read,
                unsigned long lookahead_size)
 {
@@ -166,7 +164,7 @@ unsigned int __do_page_cache_readahead(struct address_space *mapping,
        gfp_t gfp_mask = readahead_gfp_mask(mapping);
 
        if (isize == 0)
-               goto out;
+               return;
 
        end_index = ((isize - 1) >> PAGE_SHIFT);
 
@@ -211,23 +209,21 @@ unsigned int __do_page_cache_readahead(struct address_space *mapping,
        if (nr_pages)
                read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
        BUG_ON(!list_empty(&page_pool));
-out:
-       return nr_pages;
 }
 
 /*
  * Chunk the readahead into 2 megabyte units, so that we don't pin too much
  * memory at once.
  */
-int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
-                              pgoff_t offset, unsigned long nr_to_read)
+void force_page_cache_readahead(struct address_space *mapping,
+               struct file *filp, pgoff_t offset, unsigned long nr_to_read)
 {
        struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
        struct file_ra_state *ra = &filp->f_ra;
        unsigned long max_pages;
 
        if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages))
-               return -EINVAL;
+               return;
 
        /*
         * If the request exceeds the readahead window, allow the read to
@@ -245,7 +241,6 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
                offset += this_chunk;
                nr_to_read -= this_chunk;
        }
-       return 0;
 }
 
 /*
@@ -378,11 +373,10 @@ static int try_context_readahead(struct address_space *mapping,
 /*
  * A minimal readahead algorithm for trivial sequential/random reads.
  */
-static unsigned long
-ondemand_readahead(struct address_space *mapping,
-                  struct file_ra_state *ra, struct file *filp,
-                  bool hit_readahead_marker, pgoff_t offset,
-                  unsigned long req_size)
+static void ondemand_readahead(struct address_space *mapping,
+               struct file_ra_state *ra, struct file *filp,
+               bool hit_readahead_marker, pgoff_t offset,
+               unsigned long req_size)
 {
        struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
        unsigned long max_pages = ra->ra_pages;
@@ -428,7 +422,7 @@ ondemand_readahead(struct address_space *mapping,
                rcu_read_unlock();
 
                if (!start || start - offset > max_pages)
-                       return 0;
+                       return;
 
                ra->start = start;
                ra->size = start - offset;      /* old async_size */
@@ -464,7 +458,8 @@ ondemand_readahead(struct address_space *mapping,
         * standalone, small random read
         * Read as is, and do not pollute the readahead state.
         */
-       return __do_page_cache_readahead(mapping, filp, offset, req_size, 0);
+       __do_page_cache_readahead(mapping, filp, offset, req_size, 0);
+       return;
 
 initial_readahead:
        ra->start = offset;
@@ -489,7 +484,7 @@ readit:
                }
        }
 
-       return ra_submit(ra, mapping, filp);
+       ra_submit(ra, mapping, filp);
 }
 
 /**