Commit ec00b5e2 authored by Jeffle Xu's avatar Jeffle Xu Committed by Gao Xiang
Browse files

erofs: add erofs_fscache_read_folios() helper 



Add erofs_fscache_read_folios() helper reading from fscache. It supports
on-demand read semantics. That is, it will make the backend prepare for
the data when cache miss. Once data ready, it will read from the cache.

This helper can then be used to implement .readpage()/.readahead() of
on-demand read semantics.

Signed-off-by: default avatarJeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220425122143.56815-15-jefflexu@linux.alibaba.com


Acked-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
parent 3c265d7d

fs/erofs/fscache.c

+54 −0
Original line number Diff line number Diff line
@@ -5,6 +5,60 @@ 
#include <linux/fscache.h>

#include "internal.h"



/*

 * Read data from fscache and fill the read data into page cache described by

 * @start/len, which shall be both aligned with PAGE_SIZE. @pstart describes

 * the start physical address in the cache file.

 */

static int erofs_fscache_read_folios(struct fscache_cookie *cookie,

				     struct address_space *mapping,

				     loff_t start, size_t len,

				     loff_t pstart)

{

	enum netfs_io_source source;

	struct netfs_io_request rreq = {};

	struct netfs_io_subrequest subreq = { .rreq = &rreq, };

	struct netfs_cache_resources *cres = &rreq.cache_resources;

	struct super_block *sb = mapping->host->i_sb;

	struct iov_iter iter;

	size_t done = 0;

	int ret;



	ret = fscache_begin_read_operation(cres, cookie);

	if (ret)

		return ret;



	while (done < len) {

		subreq.start = pstart + done;

		subreq.len = len - done;

		subreq.flags = 1 << NETFS_SREQ_ONDEMAND;



		source = cres->ops->prepare_read(&subreq, LLONG_MAX);

		if (WARN_ON(subreq.len == 0))

			source = NETFS_INVALID_READ;

		if (source != NETFS_READ_FROM_CACHE) {

			erofs_err(sb, "failed to fscache prepare_read (source %d)",

				  source);

			ret = -EIO;

			goto out;

		}



		iov_iter_xarray(&iter, READ, &mapping->i_pages,

				start + done, subreq.len);

		ret = fscache_read(cres, subreq.start, &iter,

				   NETFS_READ_HOLE_FAIL, NULL, NULL);

		if (ret) {

			erofs_err(sb, "failed to fscache_read (ret %d)", ret);

			goto out;

		}



		done += subreq.len;

	}

out:

	fscache_end_operation(cres);

	return ret;

}



static const struct address_space_operations erofs_fscache_meta_aops = {

};