netfs-y := \
buffered_read.o \
buffered_write.o \
+ direct_read.o \
io.o \
iterator.o \
locking.o \
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Direct I/O support.
+ *
+ * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+#include <linux/sched/mm.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+/**
+ * netfs_unbuffered_read_iter_locked - Perform an unbuffered or direct I/O read
+ * @iocb: The I/O control descriptor describing the read
+ * @iter: The output buffer (also specifies read length)
+ *
+ * Perform an unbuffered I/O or direct I/O from the file in @iocb to the
+ * output buffer. No use is made of the pagecache.
+ *
+ * The caller must hold any appropriate locks.
+ */
+static ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter)
+{
+ struct netfs_io_request *rreq;
+ ssize_t ret;
+ size_t orig_count = iov_iter_count(iter);
+ bool async = !is_sync_kiocb(iocb);
+
+ _enter("");
+
+ if (!orig_count)
+ return 0; /* Don't update atime */
+
+ ret = kiocb_write_and_wait(iocb, orig_count);
+ if (ret < 0)
+ return ret;
+ file_accessed(iocb->ki_filp);
+
+ rreq = netfs_alloc_request(iocb->ki_filp->f_mapping, iocb->ki_filp,
+ iocb->ki_pos, orig_count,
+ NETFS_DIO_READ);
+ if (IS_ERR(rreq))
+ return PTR_ERR(rreq);
+
+ netfs_stat(&netfs_n_rh_dio_read);
+ trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_dio_read);
+
+ /* If this is an async op, we have to keep track of the destination
+ * buffer for ourselves as the caller's iterator will be trashed when
+ * we return.
+ *
+ * In such a case, extract an iterator to represent as much of the the
+ * output buffer as we can manage. Note that the extraction might not
+ * be able to allocate a sufficiently large bvec array and may shorten
+ * the request.
+ */
+ if (user_backed_iter(iter)) {
+ ret = netfs_extract_user_iter(iter, rreq->len, &rreq->iter, 0);
+ if (ret < 0)
+ goto out;
+ rreq->direct_bv = (struct bio_vec *)rreq->iter.bvec;
+ rreq->direct_bv_count = ret;
+ rreq->direct_bv_unpin = iov_iter_extract_will_pin(iter);
+ rreq->len = iov_iter_count(&rreq->iter);
+ } else {
+ rreq->iter = *iter;
+ rreq->len = orig_count;
+ rreq->direct_bv_unpin = false;
+ iov_iter_advance(iter, orig_count);
+ }
+
+ // TODO: Set up bounce buffer if needed
+
+ if (async)
+ rreq->iocb = iocb;
+
+ ret = netfs_begin_read(rreq, is_sync_kiocb(iocb));
+ if (ret < 0)
+ goto out; /* May be -EIOCBQUEUED */
+ if (!async) {
+ // TODO: Copy from bounce buffer
+ iocb->ki_pos += rreq->transferred;
+ ret = rreq->transferred;
+ }
+
+out:
+ netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
+ if (ret > 0)
+ orig_count -= ret;
+ if (ret != -EIOCBQUEUED)
+ iov_iter_revert(iter, orig_count - iov_iter_count(iter));
+ return ret;
+}
+
+/**
+ * netfs_unbuffered_read_iter - Perform an unbuffered or direct I/O read
+ * @iocb: The I/O control descriptor describing the read
+ * @iter: The output buffer (also specifies read length)
+ *
+ * Perform an unbuffered I/O or direct I/O from the file in @iocb to the
+ * output buffer. No use is made of the pagecache.
+ */
+ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ ssize_t ret;
+
+ if (!iter->count)
+ return 0; /* Don't update atime */
+
+ ret = netfs_start_io_direct(inode);
+ if (ret == 0) {
+ ret = netfs_unbuffered_read_iter_locked(iocb, iter);
+ netfs_end_io_direct(inode);
+ }
+ return ret;
+}
+EXPORT_SYMBOL(netfs_unbuffered_read_iter);
* stats.c
*/
#ifdef CONFIG_NETFS_STATS
+extern atomic_t netfs_n_rh_dio_read;
extern atomic_t netfs_n_rh_readahead;
extern atomic_t netfs_n_rh_readpage;
extern atomic_t netfs_n_rh_rreq;
struct netfs_io_subrequest *subreq)
{
netfs_stat(&netfs_n_rh_download);
- if (iov_iter_count(&subreq->io_iter) != subreq->len - subreq->transferred)
+
+ if (rreq->origin != NETFS_DIO_READ &&
+ iov_iter_count(&subreq->io_iter) != subreq->len - subreq->transferred)
pr_warn("R=%08x[%u] ITER PRE-MISMATCH %zx != %zx-%zx %lx\n",
rreq->debug_id, subreq->debug_index,
iov_iter_count(&subreq->io_iter), subreq->len,
}
}
+/*
+ * Determine how much we can admit to having read from a DIO read.
+ */
+static void netfs_rreq_assess_dio(struct netfs_io_request *rreq)
+{
+ struct netfs_io_subrequest *subreq;
+ unsigned int i;
+ size_t transferred = 0;
+
+ for (i = 0; i < rreq->direct_bv_count; i++)
+ flush_dcache_page(rreq->direct_bv[i].bv_page);
+
+ list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+ if (subreq->error || subreq->transferred == 0)
+ break;
+ transferred += subreq->transferred;
+ if (subreq->transferred < subreq->len)
+ break;
+ }
+
+ for (i = 0; i < rreq->direct_bv_count; i++)
+ flush_dcache_page(rreq->direct_bv[i].bv_page);
+
+ rreq->transferred = transferred;
+ task_io_account_read(transferred);
+
+ if (rreq->iocb) {
+ rreq->iocb->ki_pos += transferred;
+ if (rreq->iocb->ki_complete)
+ rreq->iocb->ki_complete(
+ rreq->iocb, rreq->error ? rreq->error : transferred);
+ }
+ if (rreq->netfs_ops->done)
+ rreq->netfs_ops->done(rreq);
+ inode_dio_end(rreq->inode);
+}
+
/*
* Assess the state of a read request and decide what to do next.
*
return;
}
- netfs_rreq_unlock_folios(rreq);
+ if (rreq->origin != NETFS_DIO_READ)
+ netfs_rreq_unlock_folios(rreq);
+ else
+ netfs_rreq_assess_dio(rreq);
trace_netfs_rreq(rreq, netfs_rreq_trace_wake_ip);
clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
struct netfs_io_subrequest *subreq,
struct iov_iter *io_iter)
{
- enum netfs_io_source source;
+ enum netfs_io_source source = NETFS_DOWNLOAD_FROM_SERVER;
size_t lsize;
_enter("%llx-%llx,%llx", subreq->start, subreq->start + subreq->len, rreq->i_size);
- source = netfs_cache_prepare_read(subreq, rreq->i_size);
- if (source == NETFS_INVALID_READ)
- goto out;
+ if (rreq->origin != NETFS_DIO_READ) {
+ source = netfs_cache_prepare_read(subreq, rreq->i_size);
+ if (source == NETFS_INVALID_READ)
+ goto out;
+ }
if (source == NETFS_DOWNLOAD_FROM_SERVER) {
/* Call out to the netfs to let it shrink the request to fit
*/
if (subreq->len > rreq->i_size - subreq->start)
subreq->len = rreq->i_size - subreq->start;
+ if (rreq->rsize && subreq->len > rreq->rsize)
+ subreq->len = rreq->rsize;
if (rreq->netfs_ops->clamp_length &&
!rreq->netfs_ops->clamp_length(subreq)) {
return -EIO;
}
+ if (rreq->origin == NETFS_DIO_READ)
+ inode_dio_begin(rreq->inode);
+
+ // TODO: Use bounce buffer if requested
rreq->io_iter = rreq->iter;
INIT_WORK(&rreq->work, netfs_rreq_work);
atomic_set(&rreq->nr_outstanding, 1);
io_iter = rreq->io_iter;
do {
+ _debug("submit %llx + %zx >= %llx",
+ rreq->start, rreq->submitted, rreq->i_size);
+ if (rreq->origin == NETFS_DIO_READ &&
+ rreq->start + rreq->submitted >= rreq->i_size)
+ break;
if (!netfs_rreq_submit_slice(rreq, &io_iter, &debug_index))
break;
+ if (test_bit(NETFS_RREQ_BLOCKED, &rreq->flags) &&
+ test_bit(NETFS_RREQ_NONBLOCK, &rreq->flags))
+ break;
} while (rreq->submitted < rreq->len);
+ if (!rreq->submitted) {
+ netfs_put_request(rreq, false, netfs_rreq_trace_put_no_submit);
+ ret = 0;
+ goto out;
+ }
+
if (sync) {
/* Keep nr_outstanding incremented so that the ref always
* belongs to us, and the service code isn't punted off to a
TASK_UNINTERRUPTIBLE);
ret = rreq->error;
- if (ret == 0 && rreq->submitted < rreq->len) {
+ if (ret == 0 && rreq->submitted < rreq->len &&
+ rreq->origin != NETFS_DIO_READ) {
trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_read);
ret = -EIO;
}
/* If we decrement nr_outstanding to 0, the ref belongs to us. */
if (atomic_dec_and_test(&rreq->nr_outstanding))
netfs_rreq_assess(rreq, false);
- ret = 0;
+ ret = -EIOCBQUEUED;
}
+
+out:
return ret;
}
[NETFS_READPAGE] = "RP",
[NETFS_READ_FOR_WRITE] = "RW",
[NETFS_WRITEBACK] = "WB",
+ [NETFS_DIO_READ] = "DR",
};
/*
struct inode *inode = file ? file_inode(file) : mapping->host;
struct netfs_inode *ctx = netfs_inode(inode);
struct netfs_io_request *rreq;
- bool cached = netfs_is_cache_enabled(ctx);
+ bool is_dio = (origin == NETFS_DIO_READ);
+ bool cached = is_dio && netfs_is_cache_enabled(ctx);
int ret;
rreq = kzalloc(ctx->ops->io_request_size ?: sizeof(struct netfs_io_request),
__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
if (cached)
__set_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
+ if (file && file->f_flags & O_NONBLOCK)
+ __set_bit(NETFS_RREQ_NONBLOCK, &rreq->flags);
if (rreq->netfs_ops->init_request) {
ret = rreq->netfs_ops->init_request(rreq, file);
if (ret < 0) {
#include <linux/seq_file.h>
#include "internal.h"
+atomic_t netfs_n_rh_dio_read;
atomic_t netfs_n_rh_readahead;
atomic_t netfs_n_rh_readpage;
atomic_t netfs_n_rh_rreq;
int netfs_stats_show(struct seq_file *m, void *v)
{
- seq_printf(m, "Netfs : RA=%u RP=%u WB=%u WBZ=%u rr=%u sr=%u\n",
+ seq_printf(m, "Netfs : DR=%u RA=%u RP=%u WB=%u WBZ=%u rr=%u sr=%u\n",
+ atomic_read(&netfs_n_rh_dio_read),
atomic_read(&netfs_n_rh_readahead),
atomic_read(&netfs_n_rh_readpage),
atomic_read(&netfs_n_rh_write_begin),
NETFS_READPAGE, /* This read is a synchronous read */
NETFS_READ_FOR_WRITE, /* This read is to prepare a write */
NETFS_WRITEBACK, /* This write was triggered by writepages */
+ NETFS_DIO_READ, /* This is a direct I/O read */
nr__netfs_io_origin
} __mode(byte);
};
struct inode *inode; /* The file being accessed */
struct address_space *mapping; /* The mapping being accessed */
+ struct kiocb *iocb; /* AIO completion vector */
struct netfs_cache_resources cache_resources;
struct list_head proc_link; /* Link in netfs_iorequests */
struct list_head subrequests; /* Contributory I/O operations */
struct bio_vec *direct_bv; /* DIO buffer list (when handling iovec-iter) */
unsigned int direct_bv_count; /* Number of elements in direct_bv[] */
unsigned int debug_id;
+ unsigned int rsize; /* Maximum read size (0 for none) */
unsigned int wsize; /* Maximum write size (0 for none) */
unsigned int subreq_counter; /* Next subreq->debug_index */
atomic_t nr_outstanding; /* Number of ops in progress */
atomic_t nr_copy_ops; /* Number of copy-to-cache ops in progress */
size_t submitted; /* Amount submitted for I/O so far */
size_t len; /* Length of the request */
+ size_t transferred; /* Amount to be indicated as transferred */
short error; /* 0 or error that occurred */
enum netfs_io_origin origin; /* Origin of the request */
bool direct_bv_unpin; /* T if direct_bv[] must be unpinned */
#define NETFS_RREQ_IN_PROGRESS 5 /* Unlocked when the request completes */
#define NETFS_RREQ_WRITE_TO_CACHE 7 /* Need to write to the cache */
#define NETFS_RREQ_UPLOAD_TO_SERVER 8 /* Need to write to the server */
+#define NETFS_RREQ_NONBLOCK 9 /* Don't block if possible (O_NONBLOCK) */
+#define NETFS_RREQ_BLOCKED 10 /* We blocked */
const struct netfs_request_ops *netfs_ops;
void (*cleanup)(struct netfs_io_request *req);
};
loff_t *_data_start, size_t *_data_len);
};
+/* High-level read API. */
+ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
+
/* High-level write API */
ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
struct netfs_group *netfs_group);
* Define enums for tracing information.
*/
#define netfs_read_traces \
+ EM(netfs_read_trace_dio_read, "DIO-READ ") \
EM(netfs_read_trace_expanded, "EXPANDED ") \
EM(netfs_read_trace_readahead, "READAHEAD") \
EM(netfs_read_trace_readpage, "READPAGE ") \
EM(NETFS_READAHEAD, "RA") \
EM(NETFS_READPAGE, "RP") \
EM(NETFS_READ_FOR_WRITE, "RW") \
- E_(NETFS_WRITEBACK, "WB")
+ EM(NETFS_WRITEBACK, "WB") \
+ E_(NETFS_DIO_READ, "DR")
#define netfs_rreq_traces \
EM(netfs_rreq_trace_assess, "ASSESS ") \
#define netfs_failures \
EM(netfs_fail_check_write_begin, "check-write-begin") \
EM(netfs_fail_copy_to_cache, "copy-to-cache") \
+ EM(netfs_fail_dio_read_short, "dio-read-short") \
+ EM(netfs_fail_dio_read_zero, "dio-read-zero") \
EM(netfs_fail_read, "read") \
EM(netfs_fail_short_read, "short-read") \
EM(netfs_fail_prepare_write, "prep-write") \
EM(netfs_rreq_trace_put_complete, "PUT COMPLT ") \
EM(netfs_rreq_trace_put_discard, "PUT DISCARD") \
EM(netfs_rreq_trace_put_failed, "PUT FAILED ") \
+ EM(netfs_rreq_trace_put_no_submit, "PUT NO-SUBM") \
EM(netfs_rreq_trace_put_return, "PUT RETURN ") \
EM(netfs_rreq_trace_put_subreq, "PUT SUBREQ ") \
EM(netfs_rreq_trace_put_work, "PUT WORK ") \
return filemap_write_and_wait_range(mapping, pos, end);
}
+EXPORT_SYMBOL_GPL(kiocb_write_and_wait);
int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
{
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