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authorMatthew Wilcox (Oracle) <willy@infradead.org>2020-06-02 07:46:51 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 20:59:06 +0300
commit2c684234d36f7e8c80414e4a772911d407e821fa (patch)
treefa1542af0f9bc1c502e81dae66d17e4c7674d237 /mm/readahead.c
parentb0f31d78cbc191058e654c8eb062a864b6c9a7eb (diff)
downloadlinux-2c684234d36f7e8c80414e4a772911d407e821fa.tar.xz
mm: add page_cache_readahead_unbounded
ext4 and f2fs have duplicated the guts of the readahead code so they can read past i_size. Instead, separate out the guts of the readahead code so they can call it directly. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Cc: Chao Yu <yuchao0@huawei.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Dave Chinner <dchinner@redhat.com> Cc: Gao Xiang <gaoxiang25@huawei.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: John Hubbard <jhubbard@nvidia.com> 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/20200414150233.24495-14-willy@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/readahead.c')
-rw-r--r--mm/readahead.c68
1 files changed, 47 insertions, 21 deletions
diff --git a/mm/readahead.c b/mm/readahead.c
index 998fdd23c0b1..ae231a5312cb 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -156,37 +156,34 @@ out:
rac->_index++;
}
-/*
- * __do_page_cache_readahead() actually reads a chunk of disk. It allocates
- * 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.
+/**
+ * page_cache_readahead_unbounded - Start unchecked readahead.
+ * @mapping: File address space.
+ * @file: This instance of the open file; used for authentication.
+ * @index: First page index to read.
+ * @nr_to_read: The number of pages to read.
+ * @lookahead_size: Where to start the next readahead.
+ *
+ * This function is for filesystems to call when they want to start
+ * readahead beyond a file's stated i_size. This is almost certainly
+ * not the function you want to call. Use page_cache_async_readahead()
+ * or page_cache_sync_readahead() instead.
+ *
+ * Context: File is referenced by caller. Mutexes may be held by caller.
+ * May sleep, but will not reenter filesystem to reclaim memory.
*/
-void __do_page_cache_readahead(struct address_space *mapping,
- struct file *filp, pgoff_t index, unsigned long nr_to_read,
+void page_cache_readahead_unbounded(struct address_space *mapping,
+ struct file *file, pgoff_t index, unsigned long nr_to_read,
unsigned long lookahead_size)
{
- struct inode *inode = mapping->host;
LIST_HEAD(page_pool);
- loff_t isize = i_size_read(inode);
gfp_t gfp_mask = readahead_gfp_mask(mapping);
struct readahead_control rac = {
.mapping = mapping,
- .file = filp,
+ .file = file,
._index = index,
};
unsigned long i;
- pgoff_t end_index; /* The last page we want to read */
-
- if (isize == 0)
- return;
-
- end_index = (isize - 1) >> PAGE_SHIFT;
- if (index > end_index)
- return;
- /* Don't read past the page containing the last byte of the file */
- if (nr_to_read > end_index - index)
- nr_to_read = end_index - index + 1;
/*
* Preallocate as many pages as we will need.
@@ -230,6 +227,35 @@ void __do_page_cache_readahead(struct address_space *mapping,
*/
read_pages(&rac, &page_pool, false);
}
+EXPORT_SYMBOL_GPL(page_cache_readahead_unbounded);
+
+/*
+ * __do_page_cache_readahead() actually reads a chunk of disk. It allocates
+ * 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.
+ */
+void __do_page_cache_readahead(struct address_space *mapping,
+ struct file *file, pgoff_t index, unsigned long nr_to_read,
+ unsigned long lookahead_size)
+{
+ struct inode *inode = mapping->host;
+ loff_t isize = i_size_read(inode);
+ pgoff_t end_index; /* The last page we want to read */
+
+ if (isize == 0)
+ return;
+
+ end_index = (isize - 1) >> PAGE_SHIFT;
+ if (index > end_index)
+ return;
+ /* Don't read past the page containing the last byte of the file */
+ if (nr_to_read > end_index - index)
+ nr_to_read = end_index - index + 1;
+
+ page_cache_readahead_unbounded(mapping, file, index, nr_to_read,
+ lookahead_size);
+}
/*
* Chunk the readahead into 2 megabyte units, so that we don't pin too much