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 <[email protected]> Signed-off-by: Li Wang <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
