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![Jeffle Xu](/assets/img/avatar_default.png)
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>
651 lines
17 KiB
C
651 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* kiocb-using read/write
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*
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* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/mount.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/uio.h>
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#include <linux/falloc.h>
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#include <linux/sched/mm.h>
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#include <trace/events/fscache.h>
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#include "internal.h"
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struct cachefiles_kiocb {
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struct kiocb iocb;
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refcount_t ki_refcnt;
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loff_t start;
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union {
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size_t skipped;
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size_t len;
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};
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struct cachefiles_object *object;
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netfs_io_terminated_t term_func;
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void *term_func_priv;
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bool was_async;
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unsigned int inval_counter; /* Copy of cookie->inval_counter */
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u64 b_writing;
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};
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static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
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{
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if (refcount_dec_and_test(&ki->ki_refcnt)) {
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cachefiles_put_object(ki->object, cachefiles_obj_put_ioreq);
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fput(ki->iocb.ki_filp);
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kfree(ki);
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}
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}
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/*
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* Handle completion of a read from the cache.
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*/
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static void cachefiles_read_complete(struct kiocb *iocb, long ret)
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{
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struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
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struct inode *inode = file_inode(ki->iocb.ki_filp);
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_enter("%ld", ret);
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if (ret < 0)
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trace_cachefiles_io_error(ki->object, inode, ret,
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cachefiles_trace_read_error);
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if (ki->term_func) {
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if (ret >= 0) {
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if (ki->object->cookie->inval_counter == ki->inval_counter)
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ki->skipped += ret;
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else
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ret = -ESTALE;
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}
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ki->term_func(ki->term_func_priv, ret, ki->was_async);
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}
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cachefiles_put_kiocb(ki);
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}
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/*
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* Initiate a read from the cache.
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*/
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static int cachefiles_read(struct netfs_cache_resources *cres,
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loff_t start_pos,
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struct iov_iter *iter,
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enum netfs_read_from_hole read_hole,
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netfs_io_terminated_t term_func,
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void *term_func_priv)
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{
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struct cachefiles_object *object;
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struct cachefiles_kiocb *ki;
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struct file *file;
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unsigned int old_nofs;
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ssize_t ret = -ENOBUFS;
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size_t len = iov_iter_count(iter), skipped = 0;
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if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
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goto presubmission_error;
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fscache_count_read();
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object = cachefiles_cres_object(cres);
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file = cachefiles_cres_file(cres);
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_enter("%pD,%li,%llx,%zx/%llx",
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file, file_inode(file)->i_ino, start_pos, len,
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i_size_read(file_inode(file)));
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/* If the caller asked us to seek for data before doing the read, then
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* we should do that now. If we find a gap, we fill it with zeros.
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*/
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if (read_hole != NETFS_READ_HOLE_IGNORE) {
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loff_t off = start_pos, off2;
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off2 = cachefiles_inject_read_error();
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if (off2 == 0)
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off2 = vfs_llseek(file, off, SEEK_DATA);
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if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO && off2 != -ENXIO) {
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skipped = 0;
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ret = off2;
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goto presubmission_error;
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}
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if (off2 == -ENXIO || off2 >= start_pos + len) {
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/* The region is beyond the EOF or there's no more data
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* in the region, so clear the rest of the buffer and
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* return success.
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*/
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ret = -ENODATA;
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if (read_hole == NETFS_READ_HOLE_FAIL)
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goto presubmission_error;
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iov_iter_zero(len, iter);
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skipped = len;
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ret = 0;
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goto presubmission_error;
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}
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skipped = off2 - off;
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iov_iter_zero(skipped, iter);
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}
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ret = -ENOMEM;
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ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
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if (!ki)
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goto presubmission_error;
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refcount_set(&ki->ki_refcnt, 2);
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ki->iocb.ki_filp = file;
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ki->iocb.ki_pos = start_pos + skipped;
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ki->iocb.ki_flags = IOCB_DIRECT;
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ki->iocb.ki_ioprio = get_current_ioprio();
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ki->skipped = skipped;
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ki->object = object;
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ki->inval_counter = cres->inval_counter;
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ki->term_func = term_func;
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ki->term_func_priv = term_func_priv;
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ki->was_async = true;
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if (ki->term_func)
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ki->iocb.ki_complete = cachefiles_read_complete;
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get_file(ki->iocb.ki_filp);
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cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
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trace_cachefiles_read(object, file_inode(file), ki->iocb.ki_pos, len - skipped);
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old_nofs = memalloc_nofs_save();
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ret = cachefiles_inject_read_error();
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if (ret == 0)
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ret = vfs_iocb_iter_read(file, &ki->iocb, iter);
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memalloc_nofs_restore(old_nofs);
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switch (ret) {
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case -EIOCBQUEUED:
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goto in_progress;
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case -ERESTARTSYS:
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case -ERESTARTNOINTR:
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case -ERESTARTNOHAND:
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case -ERESTART_RESTARTBLOCK:
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/* There's no easy way to restart the syscall since other AIO's
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* may be already running. Just fail this IO with EINTR.
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*/
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ret = -EINTR;
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fallthrough;
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default:
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ki->was_async = false;
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cachefiles_read_complete(&ki->iocb, ret);
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if (ret > 0)
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ret = 0;
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break;
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}
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in_progress:
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cachefiles_put_kiocb(ki);
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_leave(" = %zd", ret);
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return ret;
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presubmission_error:
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if (term_func)
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term_func(term_func_priv, ret < 0 ? ret : skipped, false);
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return ret;
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}
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/*
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* Query the occupancy of the cache in a region, returning where the next chunk
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* of data starts and how long it is.
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*/
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static int cachefiles_query_occupancy(struct netfs_cache_resources *cres,
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loff_t start, size_t len, size_t granularity,
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loff_t *_data_start, size_t *_data_len)
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{
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struct cachefiles_object *object;
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struct file *file;
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loff_t off, off2;
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*_data_start = -1;
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*_data_len = 0;
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if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
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return -ENOBUFS;
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object = cachefiles_cres_object(cres);
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file = cachefiles_cres_file(cres);
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granularity = max_t(size_t, object->volume->cache->bsize, granularity);
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_enter("%pD,%li,%llx,%zx/%llx",
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file, file_inode(file)->i_ino, start, len,
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i_size_read(file_inode(file)));
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off = cachefiles_inject_read_error();
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if (off == 0)
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off = vfs_llseek(file, start, SEEK_DATA);
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if (off == -ENXIO)
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return -ENODATA; /* Beyond EOF */
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if (off < 0 && off >= (loff_t)-MAX_ERRNO)
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return -ENOBUFS; /* Error. */
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if (round_up(off, granularity) >= start + len)
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return -ENODATA; /* No data in range */
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off2 = cachefiles_inject_read_error();
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if (off2 == 0)
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off2 = vfs_llseek(file, off, SEEK_HOLE);
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if (off2 == -ENXIO)
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return -ENODATA; /* Beyond EOF */
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if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO)
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return -ENOBUFS; /* Error. */
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/* Round away partial blocks */
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off = round_up(off, granularity);
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off2 = round_down(off2, granularity);
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if (off2 <= off)
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return -ENODATA;
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*_data_start = off;
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if (off2 > start + len)
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*_data_len = len;
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else
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*_data_len = off2 - off;
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return 0;
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}
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/*
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* Handle completion of a write to the cache.
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*/
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static void cachefiles_write_complete(struct kiocb *iocb, long ret)
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{
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struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
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struct cachefiles_object *object = ki->object;
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struct inode *inode = file_inode(ki->iocb.ki_filp);
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_enter("%ld", ret);
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/* Tell lockdep we inherited freeze protection from submission thread */
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__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
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__sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
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if (ret < 0)
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trace_cachefiles_io_error(object, inode, ret,
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cachefiles_trace_write_error);
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atomic_long_sub(ki->b_writing, &object->volume->cache->b_writing);
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set_bit(FSCACHE_COOKIE_HAVE_DATA, &object->cookie->flags);
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if (ki->term_func)
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ki->term_func(ki->term_func_priv, ret, ki->was_async);
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cachefiles_put_kiocb(ki);
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}
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/*
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* Initiate a write to the cache.
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*/
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int __cachefiles_write(struct cachefiles_object *object,
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struct file *file,
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loff_t start_pos,
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struct iov_iter *iter,
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netfs_io_terminated_t term_func,
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void *term_func_priv)
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{
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struct cachefiles_cache *cache;
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struct cachefiles_kiocb *ki;
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struct inode *inode;
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unsigned int old_nofs;
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ssize_t ret;
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size_t len = iov_iter_count(iter);
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fscache_count_write();
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cache = object->volume->cache;
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_enter("%pD,%li,%llx,%zx/%llx",
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file, file_inode(file)->i_ino, start_pos, len,
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i_size_read(file_inode(file)));
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ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
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if (!ki) {
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if (term_func)
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term_func(term_func_priv, -ENOMEM, false);
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return -ENOMEM;
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}
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refcount_set(&ki->ki_refcnt, 2);
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ki->iocb.ki_filp = file;
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ki->iocb.ki_pos = start_pos;
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ki->iocb.ki_flags = IOCB_DIRECT | IOCB_WRITE;
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ki->iocb.ki_ioprio = get_current_ioprio();
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ki->object = object;
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ki->start = start_pos;
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ki->len = len;
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ki->term_func = term_func;
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ki->term_func_priv = term_func_priv;
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ki->was_async = true;
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ki->b_writing = (len + (1 << cache->bshift) - 1) >> cache->bshift;
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if (ki->term_func)
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ki->iocb.ki_complete = cachefiles_write_complete;
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atomic_long_add(ki->b_writing, &cache->b_writing);
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/* Open-code file_start_write here to grab freeze protection, which
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* will be released by another thread in aio_complete_rw(). Fool
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* lockdep by telling it the lock got released so that it doesn't
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* complain about the held lock when we return to userspace.
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*/
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inode = file_inode(file);
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__sb_start_write(inode->i_sb, SB_FREEZE_WRITE);
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__sb_writers_release(inode->i_sb, SB_FREEZE_WRITE);
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get_file(ki->iocb.ki_filp);
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cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
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trace_cachefiles_write(object, inode, ki->iocb.ki_pos, len);
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old_nofs = memalloc_nofs_save();
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ret = cachefiles_inject_write_error();
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if (ret == 0)
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ret = vfs_iocb_iter_write(file, &ki->iocb, iter);
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memalloc_nofs_restore(old_nofs);
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switch (ret) {
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case -EIOCBQUEUED:
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goto in_progress;
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case -ERESTARTSYS:
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case -ERESTARTNOINTR:
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case -ERESTARTNOHAND:
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case -ERESTART_RESTARTBLOCK:
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/* There's no easy way to restart the syscall since other AIO's
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* may be already running. Just fail this IO with EINTR.
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*/
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ret = -EINTR;
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fallthrough;
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default:
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ki->was_async = false;
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cachefiles_write_complete(&ki->iocb, ret);
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if (ret > 0)
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ret = 0;
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break;
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}
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in_progress:
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cachefiles_put_kiocb(ki);
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_leave(" = %zd", ret);
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return ret;
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}
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static int cachefiles_write(struct netfs_cache_resources *cres,
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loff_t start_pos,
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struct iov_iter *iter,
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netfs_io_terminated_t term_func,
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void *term_func_priv)
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{
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if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE)) {
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if (term_func)
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term_func(term_func_priv, -ENOBUFS, false);
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return -ENOBUFS;
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}
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return __cachefiles_write(cachefiles_cres_object(cres),
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cachefiles_cres_file(cres),
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start_pos, iter,
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term_func, term_func_priv);
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}
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/*
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* Prepare a read operation, shortening it to a cached/uncached
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* boundary as appropriate.
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*/
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static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
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loff_t i_size)
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{
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enum cachefiles_prepare_read_trace why;
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struct netfs_io_request *rreq = subreq->rreq;
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struct netfs_cache_resources *cres = &rreq->cache_resources;
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struct cachefiles_object *object;
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struct cachefiles_cache *cache;
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struct fscache_cookie *cookie = fscache_cres_cookie(cres);
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const struct cred *saved_cred;
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struct file *file = cachefiles_cres_file(cres);
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enum netfs_io_source ret = NETFS_DOWNLOAD_FROM_SERVER;
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loff_t off, to;
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ino_t ino = file ? file_inode(file)->i_ino : 0;
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int rc;
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_enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);
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if (subreq->start >= i_size) {
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ret = NETFS_FILL_WITH_ZEROES;
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why = cachefiles_trace_read_after_eof;
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goto out_no_object;
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}
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if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) {
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__set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
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why = cachefiles_trace_read_no_data;
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if (!test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags))
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goto out_no_object;
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}
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/* The object and the file may be being created in the background. */
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if (!file) {
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why = cachefiles_trace_read_no_file;
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if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
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goto out_no_object;
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file = cachefiles_cres_file(cres);
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if (!file)
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goto out_no_object;
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ino = file_inode(file)->i_ino;
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}
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object = cachefiles_cres_object(cres);
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cache = object->volume->cache;
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cachefiles_begin_secure(cache, &saved_cred);
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retry:
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off = cachefiles_inject_read_error();
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if (off == 0)
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off = vfs_llseek(file, subreq->start, SEEK_DATA);
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if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
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if (off == (loff_t)-ENXIO) {
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why = cachefiles_trace_read_seek_nxio;
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goto download_and_store;
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}
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trace_cachefiles_io_error(object, file_inode(file), off,
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cachefiles_trace_seek_error);
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why = cachefiles_trace_read_seek_error;
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goto out;
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}
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if (off >= subreq->start + subreq->len) {
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why = cachefiles_trace_read_found_hole;
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goto download_and_store;
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}
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if (off > subreq->start) {
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off = round_up(off, cache->bsize);
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subreq->len = off - subreq->start;
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why = cachefiles_trace_read_found_part;
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goto download_and_store;
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}
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|
|
to = cachefiles_inject_read_error();
|
|
if (to == 0)
|
|
to = vfs_llseek(file, subreq->start, SEEK_HOLE);
|
|
if (to < 0 && to >= (loff_t)-MAX_ERRNO) {
|
|
trace_cachefiles_io_error(object, file_inode(file), to,
|
|
cachefiles_trace_seek_error);
|
|
why = cachefiles_trace_read_seek_error;
|
|
goto out;
|
|
}
|
|
|
|
if (to < subreq->start + subreq->len) {
|
|
if (subreq->start + subreq->len >= i_size)
|
|
to = round_up(to, cache->bsize);
|
|
else
|
|
to = round_down(to, cache->bsize);
|
|
subreq->len = to - subreq->start;
|
|
}
|
|
|
|
why = cachefiles_trace_read_have_data;
|
|
ret = NETFS_READ_FROM_CACHE;
|
|
goto out;
|
|
|
|
download_and_store:
|
|
__set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
|
|
if (test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags)) {
|
|
rc = cachefiles_ondemand_read(object, subreq->start,
|
|
subreq->len);
|
|
if (!rc) {
|
|
__clear_bit(NETFS_SREQ_ONDEMAND, &subreq->flags);
|
|
goto retry;
|
|
}
|
|
ret = NETFS_INVALID_READ;
|
|
}
|
|
out:
|
|
cachefiles_end_secure(cache, saved_cred);
|
|
out_no_object:
|
|
trace_cachefiles_prep_read(subreq, ret, why, ino);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Prepare for a write to occur.
|
|
*/
|
|
int __cachefiles_prepare_write(struct cachefiles_object *object,
|
|
struct file *file,
|
|
loff_t *_start, size_t *_len,
|
|
bool no_space_allocated_yet)
|
|
{
|
|
struct cachefiles_cache *cache = object->volume->cache;
|
|
loff_t start = *_start, pos;
|
|
size_t len = *_len, down;
|
|
int ret;
|
|
|
|
/* Round to DIO size */
|
|
down = start - round_down(start, PAGE_SIZE);
|
|
*_start = start - down;
|
|
*_len = round_up(down + len, PAGE_SIZE);
|
|
|
|
/* We need to work out whether there's sufficient disk space to perform
|
|
* the write - but we can skip that check if we have space already
|
|
* allocated.
|
|
*/
|
|
if (no_space_allocated_yet)
|
|
goto check_space;
|
|
|
|
pos = cachefiles_inject_read_error();
|
|
if (pos == 0)
|
|
pos = vfs_llseek(file, *_start, SEEK_DATA);
|
|
if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
|
|
if (pos == -ENXIO)
|
|
goto check_space; /* Unallocated tail */
|
|
trace_cachefiles_io_error(object, file_inode(file), pos,
|
|
cachefiles_trace_seek_error);
|
|
return pos;
|
|
}
|
|
if ((u64)pos >= (u64)*_start + *_len)
|
|
goto check_space; /* Unallocated region */
|
|
|
|
/* We have a block that's at least partially filled - if we're low on
|
|
* space, we need to see if it's fully allocated. If it's not, we may
|
|
* want to cull it.
|
|
*/
|
|
if (cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
|
|
cachefiles_has_space_check) == 0)
|
|
return 0; /* Enough space to simply overwrite the whole block */
|
|
|
|
pos = cachefiles_inject_read_error();
|
|
if (pos == 0)
|
|
pos = vfs_llseek(file, *_start, SEEK_HOLE);
|
|
if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
|
|
trace_cachefiles_io_error(object, file_inode(file), pos,
|
|
cachefiles_trace_seek_error);
|
|
return pos;
|
|
}
|
|
if ((u64)pos >= (u64)*_start + *_len)
|
|
return 0; /* Fully allocated */
|
|
|
|
/* Partially allocated, but insufficient space: cull. */
|
|
fscache_count_no_write_space();
|
|
ret = cachefiles_inject_remove_error();
|
|
if (ret == 0)
|
|
ret = vfs_fallocate(file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
|
|
*_start, *_len);
|
|
if (ret < 0) {
|
|
trace_cachefiles_io_error(object, file_inode(file), ret,
|
|
cachefiles_trace_fallocate_error);
|
|
cachefiles_io_error_obj(object,
|
|
"CacheFiles: fallocate failed (%d)\n", ret);
|
|
ret = -EIO;
|
|
}
|
|
|
|
return ret;
|
|
|
|
check_space:
|
|
return cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
|
|
cachefiles_has_space_for_write);
|
|
}
|
|
|
|
static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
|
|
loff_t *_start, size_t *_len, loff_t i_size,
|
|
bool no_space_allocated_yet)
|
|
{
|
|
struct cachefiles_object *object = cachefiles_cres_object(cres);
|
|
struct cachefiles_cache *cache = object->volume->cache;
|
|
const struct cred *saved_cred;
|
|
int ret;
|
|
|
|
if (!cachefiles_cres_file(cres)) {
|
|
if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE))
|
|
return -ENOBUFS;
|
|
if (!cachefiles_cres_file(cres))
|
|
return -ENOBUFS;
|
|
}
|
|
|
|
cachefiles_begin_secure(cache, &saved_cred);
|
|
ret = __cachefiles_prepare_write(object, cachefiles_cres_file(cres),
|
|
_start, _len,
|
|
no_space_allocated_yet);
|
|
cachefiles_end_secure(cache, saved_cred);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Clean up an operation.
|
|
*/
|
|
static void cachefiles_end_operation(struct netfs_cache_resources *cres)
|
|
{
|
|
struct file *file = cachefiles_cres_file(cres);
|
|
|
|
if (file)
|
|
fput(file);
|
|
fscache_end_cookie_access(fscache_cres_cookie(cres), fscache_access_io_end);
|
|
}
|
|
|
|
static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
|
|
.end_operation = cachefiles_end_operation,
|
|
.read = cachefiles_read,
|
|
.write = cachefiles_write,
|
|
.prepare_read = cachefiles_prepare_read,
|
|
.prepare_write = cachefiles_prepare_write,
|
|
.query_occupancy = cachefiles_query_occupancy,
|
|
};
|
|
|
|
/*
|
|
* Open the cache file when beginning a cache operation.
|
|
*/
|
|
bool cachefiles_begin_operation(struct netfs_cache_resources *cres,
|
|
enum fscache_want_state want_state)
|
|
{
|
|
struct cachefiles_object *object = cachefiles_cres_object(cres);
|
|
|
|
if (!cachefiles_cres_file(cres)) {
|
|
cres->ops = &cachefiles_netfs_cache_ops;
|
|
if (object->file) {
|
|
spin_lock(&object->lock);
|
|
if (!cres->cache_priv2 && object->file)
|
|
cres->cache_priv2 = get_file(object->file);
|
|
spin_unlock(&object->lock);
|
|
}
|
|
}
|
|
|
|
if (!cachefiles_cres_file(cres) && want_state != FSCACHE_WANT_PARAMS) {
|
|
pr_err("failed to get cres->file\n");
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|