Quelle  fscache_io.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-or-later
/* Cache data I/O routines
 *
 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */
#define FSCACHE_DEBUG_LEVEL OPERATION
#include <linux/fscache-cache.h>
#include <linux/uio.h>
#include <linux/bvec.h>
#include <linux/slab.h>
#include "internal.h"

/**
 * fscache_wait_for_operation - Wait for an object become accessible
 * @cres: The cache resources for the operation being performed
 * @want_state: The minimum state the object must be at
 *
 * See if the target cache object is at the specified minimum state of
 * accessibility yet, and if not, wait for it.
 */
bool fscache_wait_for_operation(struct netfs_cache_resources *cres,
    enum fscache_want_state want_state)
{
 struct fscache_cookie *cookie = fscache_cres_cookie(cres);
 enum fscache_cookie_state state;

again:
 if (!fscache_cache_is_live(cookie->volume->cache)) {
  _leave(" [broken]");
  return false;
 }

 state = fscache_cookie_state(cookie);
 _enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);

 switch (state) {
 case FSCACHE_COOKIE_STATE_CREATING:
 case FSCACHE_COOKIE_STATE_INVALIDATING:
  if (want_state == FSCACHE_WANT_PARAMS)
   goto ready; /* There can be no content */
  fallthrough;
 case FSCACHE_COOKIE_STATE_LOOKING_UP:
 case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
  wait_var_event(&cookie->state,
          fscache_cookie_state(cookie) != state);
  goto again;

 case FSCACHE_COOKIE_STATE_ACTIVE:
  goto ready;
 case FSCACHE_COOKIE_STATE_DROPPED:
 case FSCACHE_COOKIE_STATE_RELINQUISHING:
 default:
  _leave(" [not live]");
  return false;
 }

ready:
 if (!cres->cache_priv2)
  return cookie->volume->cache->ops->begin_operation(cres, want_state);
 return true;
}
EXPORT_SYMBOL(fscache_wait_for_operation);

/*
 * Begin an I/O operation on the cache, waiting till we reach the right state.
 *
 * Attaches the resources required to the operation resources record.
 */
static int fscache_begin_operation(struct netfs_cache_resources *cres,
       struct fscache_cookie *cookie,
       enum fscache_want_state want_state,
       enum fscache_access_trace why)
{
 enum fscache_cookie_state state;
 long timeo;
 bool once_only = false;

 cres->ops  = NULL;
 cres->cache_priv = cookie;
 cres->cache_priv2 = NULL;
 cres->debug_id  = cookie->debug_id;
 cres->inval_counter = cookie->inval_counter;

 if (!fscache_begin_cookie_access(cookie, why)) {
  cres->cache_priv = NULL;
  return -ENOBUFS;
 }

again:
 spin_lock(&cookie->lock);

 state = fscache_cookie_state(cookie);
 _enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);

 switch (state) {
 case FSCACHE_COOKIE_STATE_LOOKING_UP:
 case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
 case FSCACHE_COOKIE_STATE_INVALIDATING:
  goto wait_for_file_wrangling;
 case FSCACHE_COOKIE_STATE_CREATING:
  if (want_state == FSCACHE_WANT_PARAMS)
   goto ready; /* There can be no content */
  goto wait_for_file_wrangling;
 case FSCACHE_COOKIE_STATE_ACTIVE:
  goto ready;
 case FSCACHE_COOKIE_STATE_DROPPED:
 case FSCACHE_COOKIE_STATE_RELINQUISHING:
  WARN(1, "Can't use cookie in state %u\n", cookie->state);
  goto not_live;
 default:
  goto not_live;
 }

ready:
 spin_unlock(&cookie->lock);
 if (!cookie->volume->cache->ops->begin_operation(cres, want_state))
  goto failed;
 return 0;

wait_for_file_wrangling:
 spin_unlock(&cookie->lock);
 trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
        atomic_read(&cookie->n_accesses),
        fscache_access_io_wait);
 timeo = wait_var_event_timeout(&cookie->state,
           fscache_cookie_state(cookie) != state, 20 * HZ);
 if (timeo <= 1 && !once_only) {
  pr_warn("%s: cookie state change wait timed out: cookie->state=%u state=%u",
   __func__, fscache_cookie_state(cookie), state);
  fscache_print_cookie(cookie, 'O');
  once_only = true;
 }
 goto again;

not_live:
 spin_unlock(&cookie->lock);
failed:
 cres->cache_priv = NULL;
 cres->ops = NULL;
 fscache_end_cookie_access(cookie, fscache_access_io_not_live);
 _leave(" = -ENOBUFS");
 return -ENOBUFS;
}

int __fscache_begin_read_operation(struct netfs_cache_resources *cres,
       struct fscache_cookie *cookie)
{
 return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
           fscache_access_io_read);
}
EXPORT_SYMBOL(__fscache_begin_read_operation);

int __fscache_begin_write_operation(struct netfs_cache_resources *cres,
        struct fscache_cookie *cookie)
{
 return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
           fscache_access_io_write);
}
EXPORT_SYMBOL(__fscache_begin_write_operation);

struct fscache_write_request {
 struct netfs_cache_resources cache_resources;
 struct address_space *mapping;
 loff_t   start;
 size_t   len;
 bool   set_bits;
 bool   using_pgpriv2;
 netfs_io_terminated_t term_func;
 void   *term_func_priv;
};

void __fscache_clear_page_bits(struct address_space *mapping,
          loff_t start, size_t len)
{
 pgoff_t first = start / PAGE_SIZE;
 pgoff_t last = (start + len - 1) / PAGE_SIZE;
 struct page *page;

 if (len) {
  XA_STATE(xas, &mapping->i_pages, first);

  rcu_read_lock();
  xas_for_each(&xas, page, last) {
   folio_end_private_2(page_folio(page));
  }
  rcu_read_unlock();
 }
}
EXPORT_SYMBOL(__fscache_clear_page_bits);

/*
 * Deal with the completion of writing the data to the cache.
 */
static void fscache_wreq_done(void *priv, ssize_t transferred_or_error)
{
 struct fscache_write_request *wreq = priv;

 if (wreq->using_pgpriv2)
  fscache_clear_page_bits(wreq->mapping, wreq->start, wreq->len,
     wreq->set_bits);

 if (wreq->term_func)
  wreq->term_func(wreq->term_func_priv, transferred_or_error);
 fscache_end_operation(&wreq->cache_resources);
 kfree(wreq);
}

void __fscache_write_to_cache(struct fscache_cookie *cookie,
         struct address_space *mapping,
         loff_t start, size_t len, loff_t i_size,
         netfs_io_terminated_t term_func,
         void *term_func_priv,
         bool using_pgpriv2, bool cond)
{
 struct fscache_write_request *wreq;
 struct netfs_cache_resources *cres;
 struct iov_iter iter;
 int ret = -ENOBUFS;

 if (len == 0)
  goto abandon;

 _enter("%llx,%zx", start, len);

 wreq = kzalloc(sizeof(struct fscache_write_request), GFP_NOFS);
 if (!wreq)
  goto abandon;
 wreq->mapping  = mapping;
 wreq->start  = start;
 wreq->len  = len;
 wreq->using_pgpriv2 = using_pgpriv2;
 wreq->set_bits  = cond;
 wreq->term_func  = term_func;
 wreq->term_func_priv = term_func_priv;

 cres = &wreq->cache_resources;
 if (fscache_begin_operation(cres, cookie, FSCACHE_WANT_WRITE,
        fscache_access_io_write) < 0)
  goto abandon_free;

 ret = cres->ops->prepare_write(cres, &start, &len, len, i_size, false);
 if (ret < 0)
  goto abandon_end;

 /* TODO: Consider clearing page bits now for space the write isn't
 * covering.  This is more complicated than it appears when THPs are
 * taken into account.
 */

 iov_iter_xarray(&iter, ITER_SOURCE, &mapping->i_pages, start, len);
 fscache_write(cres, start, &iter, fscache_wreq_done, wreq);
 return;

abandon_end:
 return fscache_wreq_done(wreq, ret);
abandon_free:
 kfree(wreq);
abandon:
 if (using_pgpriv2)
  fscache_clear_page_bits(mapping, start, len, cond);
 if (term_func)
  term_func(term_func_priv, ret);
}
EXPORT_SYMBOL(__fscache_write_to_cache);

/*
 * Change the size of a backing object.
 */
void __fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)
{
 struct netfs_cache_resources cres;

 trace_fscache_resize(cookie, new_size);
 if (fscache_begin_operation(&cres, cookie, FSCACHE_WANT_WRITE,
        fscache_access_io_resize) == 0) {
  fscache_stat(&fscache_n_resizes);
  set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);

  /* We cannot defer a resize as we need to do it inside the
 * netfs's inode lock so that we're serialised with respect to
 * writes.
 */
  cookie->volume->cache->ops->resize_cookie(&cres, new_size);
  fscache_end_operation(&cres);
 } else {
  fscache_stat(&fscache_n_resizes_null);
 }
}
EXPORT_SYMBOL(__fscache_resize_cookie);