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9032b6e858
Implement the data plane of on-demand read mode. The early implementation [1] place the entry to cachefiles_ondemand_read() in fscache_read(). However, fscache_read() can only detect if the requested file range is fully cache miss, whilst we need to notify the user daemon as long as there's a hole inside the requested file range. Thus the entry is now placed in cachefiles_prepare_read(). When working in on-demand read mode, once a hole detected, the read routine will send a READ request to the user daemon. The user daemon needs to fetch the data and write it to the cache file. After sending the READ request, the read routine will hang there, until the READ request is handled by the user daemon. Then it will retry to read from the same file range. If no progress encountered, the read routine will fail then. A new NETFS_SREQ_ONDEMAND flag is introduced to indicate that on-demand read should be done when a cache miss encountered. [1] https://lore.kernel.org/all/20220406075612.60298-6-jefflexu@linux.alibaba.com/ #v8 Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Acked-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/20220425122143.56815-6-jefflexu@linux.alibaba.com Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef _LINUX_CACHEFILES_H
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#define _LINUX_CACHEFILES_H
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#include <linux/types.h>
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#include <linux/ioctl.h>
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/*
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* Fscache ensures that the maximum length of cookie key is 255. The volume key
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* is controlled by netfs, and generally no bigger than 255.
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*/
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#define CACHEFILES_MSG_MAX_SIZE 1024
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enum cachefiles_opcode {
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CACHEFILES_OP_OPEN,
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CACHEFILES_OP_CLOSE,
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CACHEFILES_OP_READ,
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};
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/*
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* Message Header
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*
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* @msg_id a unique ID identifying this message
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* @opcode message type, CACHEFILE_OP_*
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* @len message length, including message header and following data
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* @object_id a unique ID identifying a cache file
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* @data message type specific payload
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*/
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struct cachefiles_msg {
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__u32 msg_id;
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__u32 opcode;
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__u32 len;
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__u32 object_id;
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__u8 data[];
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};
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/*
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* @data contains the volume_key followed directly by the cookie_key. volume_key
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* is a NUL-terminated string; @volume_key_size indicates the size of the volume
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* key in bytes. cookie_key is binary data, which is netfs specific;
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* @cookie_key_size indicates the size of the cookie key in bytes.
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*
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* @fd identifies an anon_fd referring to the cache file.
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*/
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struct cachefiles_open {
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__u32 volume_key_size;
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__u32 cookie_key_size;
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__u32 fd;
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__u32 flags;
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__u8 data[];
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};
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/*
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* @off indicates the starting offset of the requested file range
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* @len indicates the length of the requested file range
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*/
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struct cachefiles_read {
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__u64 off;
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__u64 len;
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};
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/*
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* Reply for READ request
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* @arg for this ioctl is the @id field of READ request.
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*/
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#define CACHEFILES_IOC_READ_COMPLETE _IOW(0x98, 1, int)
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#endif
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