Enable ceph to capture stride readahead, the algorithm is simple and
straightforward: prefetch the next stripe if hit. In the future, it
may be implemented as enabled only when user requests explicitly as a
mount option.
Signed-off-by: Yunchuan Wen <yunchuanwen@xxxxxxxxxxxxxxx>
Signed-off-by: Li Wang <liwang@xxxxxxxxxxxxxxx>
---
fs/ceph/file.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
fs/ceph/super.h | 8 ++++++++
2 files changed, 67 insertions(+), 1 deletion(-)
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 3de8982..16a3981 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -9,6 +9,7 @@
#include <linux/writeback.h>
#include <linux/aio.h>
#include <linux/falloc.h>
+#include <linux/blkdev.h>
#include "super.h"
#include "mds_client.h"
@@ -635,6 +636,60 @@ out:
return ret;
}
+static void ceph_stride_readahead(struct file *file, loff_t pos, size_t length)
+{
+ struct address_space *mapping = file->f_mapping;
+ struct ceph_file_info *fi = file->private_data;
+ struct ceph_file_stride_ra_info *info = &fi->stride;
+ struct blk_plug plug;
+ LIST_HEAD(page_pool);
+ loff_t next_pos;
+ pgoff_t start, end, page_idx;
+ unsigned int nr_pages = 0;
+
+ if (info->length != length)
+ goto skip;
+ if (pos != info->pos + info->stride)
+ goto skip;
+
+ next_pos = pos + info->stride;
+ start = next_pos >> PAGE_CACHE_SHIFT;
+ end = (next_pos + length - 1) >> PAGE_CACHE_SHIFT;
+ end = min(end, start + file->f_ra.ra_pages);
+
+ for (page_idx = start; page_idx <= end; ++page_idx) {
+ struct page *page;
+
+ rcu_read_lock();
+ page = radix_tree_lookup(&mapping->page_tree, page_idx);
+ rcu_read_unlock();
+
+ if (page)
+ continue;
+
+ page = page_cache_alloc_readahead(mapping);
+ if (!page)
+ break;
+ page->index = page_idx;
+ list_add(&page->lru, &page_pool);
+
+ ++nr_pages;
+ }
+
+ if (!nr_pages)
+ goto skip;
+
+ blk_start_plug(&plug);
+ mapping->a_ops->readpages(file, mapping, &page_pool, nr_pages);
+ put_pages_list(&page_pool);
+ blk_finish_plug(&plug);
+
+skip:
+ info->length = length;
+ info->stride = pos - info->pos;
+ info->pos = pos;
+}
+
/*
* Wrap generic_file_aio_read with checks for cap bits on the inode.
* Atomically grab references, so that those bits are not released
@@ -675,8 +730,11 @@ again:
(fi->flags & CEPH_F_SYNC))
/* hmm, this isn't really async... */
ret = ceph_sync_read(filp, base, len, ppos, &checkeof);
- else
+ else {
ret = generic_file_aio_read(iocb, iov, nr_segs, pos);
+ if (ret >= 0)
+ ceph_stride_readahead(filp, pos, iocb->ki_nbytes);
+ }
out:
dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 6014b0a..72b4382 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -567,6 +567,12 @@ extern void ceph_reservation_status(struct ceph_fs_client *client,
#define CEPH_F_SYNC 1
#define CEPH_F_ATEND 2
+struct ceph_file_stride_ra_info {
+ loff_t pos;
+ size_t length;
+ loff_t stride;
+};
+
struct ceph_file_info {
short fmode; /* initialized on open */
short flags; /* CEPH_F_* */
@@ -585,6 +591,8 @@ struct ceph_file_info {
/* used for -o dirstat read() on directory thing */
char *dir_info;
int dir_info_len;
+
+ struct ceph_file_stride_ra_info stride;
};
--
1.7.9.5
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