linux/fs/cachefiles/io.c

421 lines
10 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* kiocb-using read/write
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/sched/mm.h>
#include <linux/netfs.h>
#include "internal.h"
struct cachefiles_kiocb {
struct kiocb iocb;
refcount_t ki_refcnt;
loff_t start;
union {
size_t skipped;
size_t len;
};
netfs_io_terminated_t term_func;
void *term_func_priv;
bool was_async;
};
static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
{
if (refcount_dec_and_test(&ki->ki_refcnt)) {
fput(ki->iocb.ki_filp);
kfree(ki);
}
}
/*
* Handle completion of a read from the cache.
*/
static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
{
struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
_enter("%ld,%ld", ret, ret2);
if (ki->term_func) {
if (ret >= 0)
ret += ki->skipped;
ki->term_func(ki->term_func_priv, ret, ki->was_async);
}
cachefiles_put_kiocb(ki);
}
/*
* Initiate a read from the cache.
*/
static int cachefiles_read(struct netfs_cache_resources *cres,
loff_t start_pos,
struct iov_iter *iter,
bool seek_data,
netfs_io_terminated_t term_func,
void *term_func_priv)
{
struct cachefiles_kiocb *ki;
struct file *file = cres->cache_priv2;
unsigned int old_nofs;
ssize_t ret = -ENOBUFS;
size_t len = iov_iter_count(iter), skipped = 0;
_enter("%pD,%li,%llx,%zx/%llx",
file, file_inode(file)->i_ino, start_pos, len,
i_size_read(file->f_inode));
/* If the caller asked us to seek for data before doing the read, then
* we should do that now. If we find a gap, we fill it with zeros.
*/
if (seek_data) {
loff_t off = start_pos, off2;
off2 = vfs_llseek(file, off, SEEK_DATA);
if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO && off2 != -ENXIO) {
skipped = 0;
ret = off2;
goto presubmission_error;
}
if (off2 == -ENXIO || off2 >= start_pos + len) {
/* The region is beyond the EOF or there's no more data
* in the region, so clear the rest of the buffer and
* return success.
*/
iov_iter_zero(len, iter);
skipped = len;
ret = 0;
goto presubmission_error;
}
skipped = off2 - off;
iov_iter_zero(skipped, iter);
}
ret = -ENOBUFS;
ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
if (!ki)
goto presubmission_error;
refcount_set(&ki->ki_refcnt, 2);
ki->iocb.ki_filp = file;
ki->iocb.ki_pos = start_pos + skipped;
ki->iocb.ki_flags = IOCB_DIRECT;
ki->iocb.ki_hint = ki_hint_validate(file_write_hint(file));
ki->iocb.ki_ioprio = get_current_ioprio();
ki->skipped = skipped;
ki->term_func = term_func;
ki->term_func_priv = term_func_priv;
ki->was_async = true;
if (ki->term_func)
ki->iocb.ki_complete = cachefiles_read_complete;
get_file(ki->iocb.ki_filp);
old_nofs = memalloc_nofs_save();
ret = vfs_iocb_iter_read(file, &ki->iocb, iter);
memalloc_nofs_restore(old_nofs);
switch (ret) {
case -EIOCBQUEUED:
goto in_progress;
case -ERESTARTSYS:
case -ERESTARTNOINTR:
case -ERESTARTNOHAND:
case -ERESTART_RESTARTBLOCK:
/* There's no easy way to restart the syscall since other AIO's
* may be already running. Just fail this IO with EINTR.
*/
ret = -EINTR;
fallthrough;
default:
ki->was_async = false;
cachefiles_read_complete(&ki->iocb, ret, 0);
if (ret > 0)
ret = 0;
break;
}
in_progress:
cachefiles_put_kiocb(ki);
_leave(" = %zd", ret);
return ret;
presubmission_error:
if (term_func)
term_func(term_func_priv, ret < 0 ? ret : skipped, false);
return ret;
}
/*
* Handle completion of a write to the cache.
*/
static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
{
struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
struct inode *inode = file_inode(ki->iocb.ki_filp);
_enter("%ld,%ld", ret, ret2);
/* Tell lockdep we inherited freeze protection from submission thread */
__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
__sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
if (ki->term_func)
ki->term_func(ki->term_func_priv, ret, ki->was_async);
cachefiles_put_kiocb(ki);
}
/*
* Initiate a write to the cache.
*/
static int cachefiles_write(struct netfs_cache_resources *cres,
loff_t start_pos,
struct iov_iter *iter,
netfs_io_terminated_t term_func,
void *term_func_priv)
{
struct cachefiles_kiocb *ki;
struct inode *inode;
struct file *file = cres->cache_priv2;
unsigned int old_nofs;
ssize_t ret = -ENOBUFS;
size_t len = iov_iter_count(iter);
_enter("%pD,%li,%llx,%zx/%llx",
file, file_inode(file)->i_ino, start_pos, len,
i_size_read(file->f_inode));
ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
if (!ki)
goto presubmission_error;
refcount_set(&ki->ki_refcnt, 2);
ki->iocb.ki_filp = file;
ki->iocb.ki_pos = start_pos;
ki->iocb.ki_flags = IOCB_DIRECT | IOCB_WRITE;
ki->iocb.ki_hint = ki_hint_validate(file_write_hint(file));
ki->iocb.ki_ioprio = get_current_ioprio();
ki->start = start_pos;
ki->len = len;
ki->term_func = term_func;
ki->term_func_priv = term_func_priv;
ki->was_async = true;
if (ki->term_func)
ki->iocb.ki_complete = cachefiles_write_complete;
/* Open-code file_start_write here to grab freeze protection, which
* will be released by another thread in aio_complete_rw(). Fool
* lockdep by telling it the lock got released so that it doesn't
* complain about the held lock when we return to userspace.
*/
inode = file_inode(file);
__sb_start_write(inode->i_sb, SB_FREEZE_WRITE);
__sb_writers_release(inode->i_sb, SB_FREEZE_WRITE);
get_file(ki->iocb.ki_filp);
old_nofs = memalloc_nofs_save();
ret = vfs_iocb_iter_write(file, &ki->iocb, iter);
memalloc_nofs_restore(old_nofs);
switch (ret) {
case -EIOCBQUEUED:
goto in_progress;
case -ERESTARTSYS:
case -ERESTARTNOINTR:
case -ERESTARTNOHAND:
case -ERESTART_RESTARTBLOCK:
/* There's no easy way to restart the syscall since other AIO's
* may be already running. Just fail this IO with EINTR.
*/
ret = -EINTR;
fallthrough;
default:
ki->was_async = false;
cachefiles_write_complete(&ki->iocb, ret, 0);
if (ret > 0)
ret = 0;
break;
}
in_progress:
cachefiles_put_kiocb(ki);
_leave(" = %zd", ret);
return ret;
presubmission_error:
if (term_func)
term_func(term_func_priv, -ENOMEM, false);
return -ENOMEM;
}
/*
* Prepare a read operation, shortening it to a cached/uncached
* boundary as appropriate.
*/
static enum netfs_read_source cachefiles_prepare_read(struct netfs_read_subrequest *subreq,
loff_t i_size)
{
struct fscache_retrieval *op = subreq->rreq->cache_resources.cache_priv;
struct cachefiles_object *object;
struct cachefiles_cache *cache;
const struct cred *saved_cred;
struct file *file = subreq->rreq->cache_resources.cache_priv2;
loff_t off, to;
_enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);
object = container_of(op->op.object,
struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);
if (!file)
goto cache_fail_nosec;
if (subreq->start >= i_size)
return NETFS_FILL_WITH_ZEROES;
cachefiles_begin_secure(cache, &saved_cred);
off = vfs_llseek(file, subreq->start, SEEK_DATA);
if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
if (off == (loff_t)-ENXIO)
goto download_and_store;
goto cache_fail;
}
if (off >= subreq->start + subreq->len)
goto download_and_store;
if (off > subreq->start) {
off = round_up(off, cache->bsize);
subreq->len = off - subreq->start;
goto download_and_store;
}
to = vfs_llseek(file, subreq->start, SEEK_HOLE);
if (to < 0 && to >= (loff_t)-MAX_ERRNO)
goto cache_fail;
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;
}
cachefiles_end_secure(cache, saved_cred);
return NETFS_READ_FROM_CACHE;
download_and_store:
if (cachefiles_has_space(cache, 0, (subreq->len + PAGE_SIZE - 1) / PAGE_SIZE) == 0)
__set_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags);
cache_fail:
cachefiles_end_secure(cache, saved_cred);
cache_fail_nosec:
return NETFS_DOWNLOAD_FROM_SERVER;
}
/*
* Prepare for a write to occur.
*/
static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
loff_t *_start, size_t *_len, loff_t i_size)
{
loff_t start = *_start;
size_t len = *_len, down;
/* Round to DIO size */
down = start - round_down(start, PAGE_SIZE);
*_start = start - down;
*_len = round_up(down + len, PAGE_SIZE);
return 0;
}
/*
* Clean up an operation.
*/
static void cachefiles_end_operation(struct netfs_cache_resources *cres)
{
struct fscache_retrieval *op = cres->cache_priv;
struct file *file = cres->cache_priv2;
_enter("");
if (file)
fput(file);
if (op) {
fscache_op_complete(&op->op, false);
fscache_put_retrieval(op);
}
_leave("");
}
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,
};
/*
* Open the cache file when beginning a cache operation.
*/
int cachefiles_begin_read_operation(struct netfs_read_request *rreq,
struct fscache_retrieval *op)
{
struct cachefiles_object *object;
struct cachefiles_cache *cache;
struct path path;
struct file *file;
_enter("");
object = container_of(op->op.object,
struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);
path.mnt = cache->mnt;
path.dentry = object->backer;
file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
d_inode(object->backer), cache->cache_cred);
if (IS_ERR(file))
return PTR_ERR(file);
if (!S_ISREG(file_inode(file)->i_mode))
goto error_file;
if (unlikely(!file->f_op->read_iter) ||
unlikely(!file->f_op->write_iter)) {
pr_notice("Cache does not support read_iter and write_iter\n");
goto error_file;
}
fscache_get_retrieval(op);
rreq->cache_resources.cache_priv = op;
rreq->cache_resources.cache_priv2 = file;
rreq->cache_resources.ops = &cachefiles_netfs_cache_ops;
rreq->cookie_debug_id = object->fscache.debug_id;
_leave("");
return 0;
error_file:
fput(file);
return -EIO;
}