mm/readahead: add DEFINE_READAHEAD

Patch series "Readahead patches for 5.9/5.10".

These are infrastructure for both the THP patchset and for the fscache
rewrite,

For both pieces of infrastructure being build on top of this patchset, we
want the ractl to be available higher in the call-stack.

For David's work, he wants to add the 'critical page' to the ractl so that
he knows which page NEEDS to be brought in from storage, and which ones
are nice-to-have.  We might want something similar in block storage too.
It used to be simple -- the first page was the critical one, but then mmap
added fault-around and so for that usecase, the middle page is the
critical one.  Anyway, I don't have any code to show that yet, we just
know that the lowest point in the callchain where we have that information
is do_sync_mmap_readahead() and so the ractl needs to start its life
there.

For THP, we havew the code that needs it.  It's actually the apex patch to
the series; the one which finally starts to allocate THPs and present them
to consenting filesystems:
http://git.infradead.org/users/willy/pagecache.git/commitdiff/798bcf30ab2eff278caad03a9edca74d2f8ae760

This patch (of 8):

Allow for a more concise definition of a struct readahead_control.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric Biggers <ebiggers@google.com>
Cc: David Howells <dhowells@redhat.com>
Link: https://lkml.kernel.org/r/20200903140844.14194-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20200903140844.14194-3-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a0024528a9eeacfde322d6577a1e045853356e9b..63c81b512e8056f8c2d2799b13a639817ce33405 100644 (file)
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -812,6 +812,13 @@ struct readahead_control {
        unsigned int _batch_count;
 };
 
+#define DEFINE_READAHEAD(rac, f, m, i)                                 \
+       struct readahead_control rac = {                                \
+               .file = f,                                              \
+               .mapping = m,                                           \
+               ._index = i,                                            \
+       }
+
 /**
  * readahead_page - Get the next page to read.
  * @rac: The current readahead request.

diff --git a/mm/readahead.c b/mm/readahead.c
index 3c9a8dd7c56c86f9b868d8d9d7e745602a38ea75..2126a2754e22c7069f87af274169bb8415c57994 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -179,11 +179,7 @@ void page_cache_readahead_unbounded(struct address_space *mapping,
 {
        LIST_HEAD(page_pool);
        gfp_t gfp_mask = readahead_gfp_mask(mapping);
-       struct readahead_control rac = {
-               .mapping = mapping,
-               .file = file,
-               ._index = index,
-       };
+       DEFINE_READAHEAD(rac, file, mapping, index);
        unsigned long i;
 
        /*