The patch titled
Subject: mm: return void from various readahead functions
has been added to the -mm tree. Its filename is
mm-return-void-from-various-readahead-functions.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-return-void-from-various-readahead-functions.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-return-void-from-various-readahead-functions.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: 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().
Link: http://lkml.kernel.org/r/20200414150233.24495-3-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Chao Yu <yuchao0@xxxxxxxxxx>
Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Gao Xiang <gaoxiang25@xxxxxxxxxx>
Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Cc: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/fadvise.c | 4 ----
mm/internal.h | 12 ++++++------
mm/readahead.c | 31 +++++++++++++------------------
3 files changed, 19 insertions(+), 28 deletions(-)
--- a/mm/fadvise.c~mm-return-void-from-various-readahead-functions
+++ a/mm/fadvise.c
@@ -104,10 +104,6 @@ int generic_fadvise(struct file *file, l
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:
--- a/mm/internal.h~mm-return-void-from-various-readahead-functions
+++ a/mm/internal.h
@@ -49,20 +49,20 @@ void unmap_page_range(struct mmu_gather
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);
}
/**
--- a/mm/readahead.c~mm-return-void-from-various-readahead-functions
+++ a/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(s
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(s
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 ad
offset += this_chunk;
nr_to_read -= this_chunk;
}
- return 0;
}
/*
@@ -378,11 +373,10 @@ static int try_context_readahead(struct
/*
* 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
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
* 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);
}
/**
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-move-readahead-prototypes-from-mmh.patch
mm-return-void-from-various-readahead-functions.patch
mm-ignore-return-value-of-readpages.patch
mm-move-readahead-nr_pages-check-into-read_pages.patch
mm-add-new-readahead_control-api.patch
mm-use-readahead_control-to-pass-arguments.patch
mm-rename-various-offset-parameters-to-index.patch
mm-rename-readahead-loop-variable-to-i.patch
mm-remove-page_offset-from-readahead-loop.patch
mm-put-readahead-pages-in-cache-earlier.patch
mm-add-readahead-address-space-operation.patch
mm-move-end_index-check-out-of-readahead-loop.patch
mm-add-page_cache_readahead_unbounded.patch
mm-document-why-we-dont-set-pagereadahead.patch
mm-use-memalloc_nofs_save-in-readahead-path.patch
fs-convert-mpage_readpages-to-mpage_readahead.patch
btrfs-convert-from-readpages-to-readahead.patch
erofs-convert-uncompressed-files-from-readpages-to-readahead.patch
erofs-convert-compressed-files-from-readpages-to-readahead.patch
ext4-convert-from-readpages-to-readahead.patch
ext4-pass-the-inode-to-ext4_mpage_readpages.patch
f2fs-convert-from-readpages-to-readahead.patch
f2fs-pass-the-inode-to-f2fs_mpage_readpages.patch
fuse-convert-from-readpages-to-readahead.patch
iomap-convert-from-readpages-to-readahead.patch
