From: Matthew Wilcox <willy@infradead.org>
To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
Jeff Layton <jlayton@kernel.org>,
Christoph Hellwig <hch@infradead.org>, Chris Mason <clm@fb.com>
Subject: [PATCH v2 5/9] mm: Add readahead address space operation
Date: Tue, 14 Jan 2020 18:38:39 -0800 [thread overview]
Message-ID: <20200115023843.31325-6-willy@infradead.org> (raw)
In-Reply-To: <20200115023843.31325-1-willy@infradead.org>
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
This replaces ->readpages with a saner interface:
- Return the number of pages not read instead of an ignored error code.
- Pages are already in the page cache when ->readahead is called.
- Implementation looks up the pages in the page cache instead of
having them passed in a linked list.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
Documentation/filesystems/locking.rst | 7 ++++++-
Documentation/filesystems/vfs.rst | 11 +++++++++++
include/linux/fs.h | 2 ++
include/linux/pagemap.h | 12 ++++++++++++
mm/readahead.c | 13 ++++++++++++-
5 files changed, 43 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index 5057e4d9dcd1..d8a5dde914b5 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -239,6 +239,8 @@ prototypes::
int (*readpage)(struct file *, struct page *);
int (*writepages)(struct address_space *, struct writeback_control *);
int (*set_page_dirty)(struct page *page);
+ unsigned (*readahead)(struct file *, struct address_space *,
+ pgoff_t start, unsigned nr_pages);
int (*readpages)(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages);
int (*write_begin)(struct file *, struct address_space *mapping,
@@ -271,7 +273,8 @@ writepage: yes, unlocks (see below)
readpage: yes, unlocks
writepages:
set_page_dirty no
-readpages:
+readahead: yes, unlocks
+readpages: no
write_begin: locks the page exclusive
write_end: yes, unlocks exclusive
bmap:
@@ -295,6 +298,8 @@ the request handler (/dev/loop).
->readpage() unlocks the page, either synchronously or via I/O
completion.
+->readahead() unlocks the page like ->readpage().
+
->readpages() populates the pagecache with the passed pages and starts
I/O against them. They come unlocked upon I/O completion.
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 7d4d09dd5e6d..bb06fb7b120b 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -706,6 +706,8 @@ cache in your filesystem. The following members are defined:
int (*readpage)(struct file *, struct page *);
int (*writepages)(struct address_space *, struct writeback_control *);
int (*set_page_dirty)(struct page *page);
+ unsigned (*readahead)(struct file *filp, struct address_space *mapping,
+ pgoff_t start, unsigned nr_pages);
int (*readpages)(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages);
int (*write_begin)(struct file *, struct address_space *mapping,
@@ -781,6 +783,15 @@ cache in your filesystem. The following members are defined:
If defined, it should set the PageDirty flag, and the
PAGECACHE_TAG_DIRTY tag in the radix tree.
+``readahead``
+ called by the VM to read pages associated with the address_space
+ object. The pages are consecutive in the page cache and are
+ locked. The implementation should decrement the page refcount after
+ attempting I/O on each page. Usually the page will be unlocked by
+ the I/O completion handler. If the function does not attempt I/O on
+ some pages, return the number of pages which were not read so the
+ common code can unlock the pages for you.
+
``readpages``
called by the VM to read pages associated with the address_space
object. This is essentially just a vector version of readpage.
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 98e0349adb52..a10f3a72e5ac 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -375,6 +375,8 @@ struct address_space_operations {
*/
int (*readpages)(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages);
+ unsigned (*readahead)(struct file *, struct address_space *,
+ pgoff_t start, unsigned nr_pages);
int (*write_begin)(struct file *, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 37a4d9e32cd3..0821f584c43c 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -630,6 +630,18 @@ static inline int add_to_page_cache(struct page *page,
return error;
}
+/*
+ * Only call this from a ->readahead implementation.
+ */
+static inline
+struct page *readahead_page(struct address_space *mapping, loff_t pos)
+{
+ struct page *page = xa_load(&mapping->i_pages, pos / PAGE_SIZE);
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+ return page;
+}
+
static inline unsigned long dir_pages(struct inode *inode)
{
return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
diff --git a/mm/readahead.c b/mm/readahead.c
index 5a6676640f20..6d65dae6dad0 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -121,7 +121,18 @@ static void read_pages(struct address_space *mapping, struct file *filp,
blk_start_plug(&plug);
- if (mapping->a_ops->readpages) {
+ if (mapping->a_ops->readahead) {
+ unsigned left = mapping->a_ops->readahead(filp, mapping,
+ start, nr_pages);
+
+ while (left) {
+ struct page *page = readahead_page(mapping,
+ start + nr_pages - left - 1);
+ unlock_page(page);
+ put_page(page);
+ left--;
+ }
+ } else if (mapping->a_ops->readpages) {
mapping->a_ops->readpages(filp, mapping, pages, nr_pages);
/* Clean up the remaining pages */
put_pages_list(pages);
--
2.24.1
next prev parent reply other threads:[~2020-01-15 2:38 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 2:38 [RFC v2 0/9] Replacing the readpages a_op Matthew Wilcox
2020-01-15 2:38 ` [PATCH v2 1/9] mm: Fix the return type of __do_page_cache_readahead Matthew Wilcox
2020-01-15 2:38 ` [PATCH v2 2/9] readahead: Ignore return value of ->readpages Matthew Wilcox
2020-01-15 2:38 ` [PATCH v2 3/9] XArray: Add xarray_for_each_range Matthew Wilcox
2020-01-15 2:38 ` [PATCH v2 4/9] readahead: Put pages in cache earlier Matthew Wilcox
2020-01-15 2:38 ` Matthew Wilcox [this message]
2020-01-15 2:38 ` [PATCH v2 6/9] iomap,xfs: Convert from readpages to readahead Matthew Wilcox
2020-01-15 7:16 ` Christoph Hellwig
2020-01-15 7:42 ` Matthew Wilcox
2020-01-24 22:53 ` Matthew Wilcox
2020-01-15 2:38 ` [PATCH v2 7/9] cifs: " Matthew Wilcox
2020-01-15 2:38 ` [PATCH v2 8/9] mm: Remove add_to_page_cache_locked Matthew Wilcox
2020-01-15 2:38 ` [PATCH v2 9/9] mm: Unify all add_to_page_cache variants Matthew Wilcox
2020-01-15 7:20 ` Christoph Hellwig
2020-01-15 7:44 ` Matthew Wilcox
2020-01-18 23:13 ` [RFC v2 0/9] Replacing the readpages a_op Matthew Wilcox
2020-01-21 11:36 ` Jan Kara
2020-01-21 21:48 ` Matthew Wilcox
2020-01-22 9:44 ` Jan Kara
2020-01-23 10:31 ` Jan Kara
2020-01-22 23:47 ` Dave Chinner
2020-01-23 10:21 ` Jan Kara
2020-01-23 22:29 ` Dave Chinner
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