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06c5c97293
When NFSD_IO_DIRECT is selected via the /sys/kernel/debug/nfsd/io_cache_write experimental tunable, split incoming unaligned NFS WRITE requests into a prefix, middle and suffix segment, as needed. The middle segment is now DIO-aligned and the prefix and/or suffix are unaligned. Synchronous buffered IO is used for the unaligned segments, and IOCB_DIRECT is used for the middle DIO-aligned extent. Although IOCB_DIRECT avoids the use of the page cache, by itself it doesn't guarantee data durability. For UNSTABLE WRITE requests, durability is obtained by a subsequent NFS COMMIT request. Signed-off-by: Mike Snitzer <snitzer@kernel.org> Co-developed-by: Chuck Lever <chuck.lever@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
144 lines
3.0 KiB
C
144 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/debugfs.h>
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#include "nfsd.h"
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static struct dentry *nfsd_top_dir __read_mostly;
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/*
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* /sys/kernel/debug/nfsd/disable-splice-read
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*
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* Contents:
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* %0: NFS READ is allowed to use page splicing
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* %1: NFS READ uses only iov iter read
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*
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* The default value of this setting is zero (page splicing is
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* allowed). This setting takes immediate effect for all NFS
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* versions, all exports, and in all NFSD net namespaces.
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*/
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static int nfsd_dsr_get(void *data, u64 *val)
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{
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*val = nfsd_disable_splice_read ? 1 : 0;
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return 0;
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}
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static int nfsd_dsr_set(void *data, u64 val)
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{
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nfsd_disable_splice_read = (val > 0);
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if (!nfsd_disable_splice_read) {
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/*
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* Must use buffered I/O if splice_read is enabled.
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*/
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nfsd_io_cache_read = NFSD_IO_BUFFERED;
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}
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return 0;
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}
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DEFINE_DEBUGFS_ATTRIBUTE(nfsd_dsr_fops, nfsd_dsr_get, nfsd_dsr_set, "%llu\n");
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/*
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* /sys/kernel/debug/nfsd/io_cache_read
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*
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* Contents:
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* %0: NFS READ will use buffered IO
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* %1: NFS READ will use dontcache (buffered IO w/ dropbehind)
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* %2: NFS READ will use direct IO
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*
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* This setting takes immediate effect for all NFS versions,
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* all exports, and in all NFSD net namespaces.
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*/
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static int nfsd_io_cache_read_get(void *data, u64 *val)
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{
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*val = nfsd_io_cache_read;
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return 0;
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}
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static int nfsd_io_cache_read_set(void *data, u64 val)
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{
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int ret = 0;
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switch (val) {
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case NFSD_IO_BUFFERED:
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nfsd_io_cache_read = NFSD_IO_BUFFERED;
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break;
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case NFSD_IO_DONTCACHE:
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case NFSD_IO_DIRECT:
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/*
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* Must disable splice_read when enabling
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* NFSD_IO_DONTCACHE.
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*/
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nfsd_disable_splice_read = true;
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nfsd_io_cache_read = val;
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break;
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default:
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ret = -EINVAL;
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break;
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}
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return ret;
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}
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DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_read_fops, nfsd_io_cache_read_get,
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nfsd_io_cache_read_set, "%llu\n");
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/*
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* /sys/kernel/debug/nfsd/io_cache_write
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*
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* Contents:
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* %0: NFS WRITE will use buffered IO
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* %1: NFS WRITE will use dontcache (buffered IO w/ dropbehind)
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*
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* This setting takes immediate effect for all NFS versions,
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* all exports, and in all NFSD net namespaces.
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*/
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static int nfsd_io_cache_write_get(void *data, u64 *val)
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{
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*val = nfsd_io_cache_write;
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return 0;
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}
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static int nfsd_io_cache_write_set(void *data, u64 val)
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{
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int ret = 0;
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switch (val) {
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case NFSD_IO_BUFFERED:
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case NFSD_IO_DONTCACHE:
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case NFSD_IO_DIRECT:
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nfsd_io_cache_write = val;
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break;
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default:
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ret = -EINVAL;
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break;
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}
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return ret;
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}
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DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_write_fops, nfsd_io_cache_write_get,
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nfsd_io_cache_write_set, "%llu\n");
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void nfsd_debugfs_exit(void)
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{
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debugfs_remove_recursive(nfsd_top_dir);
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nfsd_top_dir = NULL;
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}
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void nfsd_debugfs_init(void)
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{
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nfsd_top_dir = debugfs_create_dir("nfsd", NULL);
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debugfs_create_file("disable-splice-read", S_IWUSR | S_IRUGO,
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nfsd_top_dir, NULL, &nfsd_dsr_fops);
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debugfs_create_file("io_cache_read", 0644, nfsd_top_dir, NULL,
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&nfsd_io_cache_read_fops);
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debugfs_create_file("io_cache_write", 0644, nfsd_top_dir, NULL,
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&nfsd_io_cache_write_fops);
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}
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