fs/fscache/io.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Cache data I/O routines
   3  *
   4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #define FSCACHE_DEBUG_LEVEL PAGE
   9 #include <linux/module.h>
  10 #define FSCACHE_USE_NEW_IO_API
  11 #include <linux/fscache-cache.h>
  12 #include <linux/slab.h>
  13 #include <linux/netfs.h>
  14 #include "internal.h"
  15
  16 /*
  17  * Start a cache read operation.
  18  * - we return:
  19  *   -ENOMEM    - out of memory, some pages may be being read
  20  *   -ERESTARTSYS - interrupted, some pages may be being read
  21  *   -ENOBUFS   - no backing object or space available in which to cache any
  22  *                pages not being read
  23  *   -ENODATA   - no data available in the backing object for some or all of
  24  *                the pages
  25  *   0          - dispatched a read on all pages
  26  */
  27 int __fscache_begin_read_operation(struct netfs_read_request *rreq,
  28                                    struct fscache_cookie *cookie)
  29 {
  30         struct fscache_retrieval *op;
  31         struct fscache_object *object;
  32         bool wake_cookie = false;
  33         int ret;
  34
  35         _enter("rr=%08x", rreq->debug_id);
  36
  37         fscache_stat(&fscache_n_retrievals);
  38
  39         if (hlist_empty(&cookie->backing_objects))
  40                 goto nobufs;
  41
  42         if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
  43                 _leave(" = -ENOBUFS [invalidating]");
  44                 return -ENOBUFS;
  45         }
  46
  47         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
  48
  49         if (fscache_wait_for_deferred_lookup(cookie) < 0)
  50                 return -ERESTARTSYS;
  51
  52         op = fscache_alloc_retrieval(cookie, NULL, NULL, NULL);
  53         if (!op)
  54                 return -ENOMEM;
  55         trace_fscache_page_op(cookie, NULL, &op->op, fscache_page_op_retr_multi);
  56
  57         spin_lock(&cookie->lock);
  58
  59         if (!fscache_cookie_enabled(cookie) ||
  60             hlist_empty(&cookie->backing_objects))
  61                 goto nobufs_unlock;
  62         object = hlist_entry(cookie->backing_objects.first,
  63                              struct fscache_object, cookie_link);
  64
  65         __fscache_use_cookie(cookie);
  66         atomic_inc(&object->n_reads);
  67         __set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
  68
  69         if (fscache_submit_op(object, &op->op) < 0)
  70                 goto nobufs_unlock_dec;
  71         spin_unlock(&cookie->lock);
  72
  73         fscache_stat(&fscache_n_retrieval_ops);
  74
  75         /* we wait for the operation to become active, and then process it
  76          * *here*, in this thread, and not in the thread pool */
  77         ret = fscache_wait_for_operation_activation(
  78                 object, &op->op,
  79                 __fscache_stat(&fscache_n_retrieval_op_waits),
  80                 __fscache_stat(&fscache_n_retrievals_object_dead));
  81         if (ret < 0)
  82                 goto error;
  83
  84         /* ask the cache to honour the operation */
  85         ret = object->cache->ops->begin_read_operation(rreq, op);
  86
  87 error:
  88         if (ret == -ENOMEM)
  89                 fscache_stat(&fscache_n_retrievals_nomem);
  90         else if (ret == -ERESTARTSYS)
  91                 fscache_stat(&fscache_n_retrievals_intr);
  92         else if (ret == -ENODATA)
  93                 fscache_stat(&fscache_n_retrievals_nodata);
  94         else if (ret < 0)
  95                 fscache_stat(&fscache_n_retrievals_nobufs);
  96         else
  97                 fscache_stat(&fscache_n_retrievals_ok);
  98
  99         fscache_put_retrieval(op);
 100         _leave(" = %d", ret);
 101         return ret;
 102
 103 nobufs_unlock_dec:
 104         atomic_dec(&object->n_reads);
 105         wake_cookie = __fscache_unuse_cookie(cookie);
 106 nobufs_unlock:
 107         spin_unlock(&cookie->lock);
 108         fscache_put_retrieval(op);
 109         if (wake_cookie)
 110                 __fscache_wake_unused_cookie(cookie);
 111 nobufs:
 112         fscache_stat(&fscache_n_retrievals_nobufs);
 113         _leave(" = -ENOBUFS");
 114         return -ENOBUFS;
 115 }
 116 EXPORT_SYMBOL(__fscache_begin_read_operation);