From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 55267292B44 for ; Wed, 3 Sep 2025 20:51:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756932687; cv=none; b=cLZwIZtiuesQDzuCKkWJ2D0IiNEIJQRBw6baxt0a28H90sASAzmMI+zE4ZyWrugJqBqwpUzScngF1guaOdS9IncY0HD5du/ThskhBvpCbGvXx7ZX03FXvLCyc0GowwySl+rl4Cw/rEoQ5mXhIqf7hQnFIt9f2YYVDh+79AkTe9M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756932687; c=relaxed/simple; bh=bSSrRmOATquWkd/sIs5v/xPwzYy8SvqdL5yYkwxN5Hk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FSUJU3oVHKLLYl0jjKxRAAr+t7MzRm+k2j5bxGxj/+LwfNzY12tybUknvk4bpleVJsK9FuIIe7UPWReRwyB6AiuzezwhyEjL/mkgBx6CU39N38DpmlRtsxNwPu0d+/w5PWYDu3E6DU/pfy3M7Mj8AHrttNxTmXoOh9Fdzp5UOGg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VuXbUYdN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VuXbUYdN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99BC4C4CEE7; Wed, 3 Sep 2025 20:51:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756932686; bh=bSSrRmOATquWkd/sIs5v/xPwzYy8SvqdL5yYkwxN5Hk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VuXbUYdN+BcRFo6bgNoAhdjby7rRyyQBAU0RPRxwmg3qLLsivC2e51Oo/D2uYkmvD ttL/OIb0jfI+Twi1GBH+9QOlo/SgfFSQ+TeUXPZTOqExpku/VlGH/bEzzNmruiLk0X fDs6bJ0T+uRofsGNoD7tQqEZXHgEmdKHGqd0ZA09XBiiQSn7DiODldn4APXtLQwkIv kX+bigsY2yK17PB5dqfHSe/3YYWvyiJen+2W0VSD5jSD/4xZIexZZNK4Wg3P4oNRL7 PtJ/bVA4boJ6ambOgFHS6VA0Zzeh/XLCKP41nVVLwmGSexW+16kEyfMpYEl14MGjcs ldzaHWZvj5N4g== From: Mike Snitzer To: Chuck Lever , Jeff Layton Cc: linux-nfs@vger.kernel.org Subject: [PATCH v9 3/9] NFSD: add io_cache_read controls to debugfs interface Date: Wed, 3 Sep 2025 16:51:15 -0400 Message-ID: <20250903205121.41380-4-snitzer@kernel.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20250903205121.41380-1-snitzer@kernel.org> References: <20250903205121.41380-1-snitzer@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add 'io_cache_read' to NFSD's debugfs interface so that: Any data read by NFSD will either be: - cached using page cache (NFSD_IO_BUFFERED=0) - cached but removed from the page cache upon completion (NFSD_IO_DONTCACHE=1). - not cached (NFSD_IO_DIRECT=2) io_cache_read may be set by writing to: /sys/kernel/debug/nfsd/io_cache_read The default value for io_cache_read reflects NFSD's current default IO mode (NFSD_IO_BUFFERED=0). If NFSD_IO_DONTCACHE is specified using 1, FOP_DONTCACHE must be advertised as supported by the underlying filesystem (e.g. XFS), otherwise all IO flagged with RWF_DONTCACHE will fail with -EOPNOTSUPP. If NFSD_IO_DIRECT is specified using 2, the IO must be aligned relative to the underlying block device's logical_block_size. Also the memory buffer used to store the read must be aligned relative to the underlying block device's dma_alignment. Signed-off-by: Mike Snitzer --- fs/nfsd/debugfs.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++ fs/nfsd/nfsd.h | 9 ++++++++ fs/nfsd/vfs.c | 17 ++++++++++++++ 3 files changed, 82 insertions(+) diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c index 84b0c8b559dc9..dd1dc28a53784 100644 --- a/fs/nfsd/debugfs.c +++ b/fs/nfsd/debugfs.c @@ -27,11 +27,64 @@ static int nfsd_dsr_get(void *data, u64 *val) static int nfsd_dsr_set(void *data, u64 val) { nfsd_disable_splice_read = (val > 0) ? true : false; + if (!nfsd_disable_splice_read) { + /* + * Cannot use NFSD_IO_DONTCACHE or NFSD_IO_DIRECT + * if splice_read is enabled. + */ + nfsd_io_cache_read = NFSD_IO_BUFFERED; + } return 0; } DEFINE_DEBUGFS_ATTRIBUTE(nfsd_dsr_fops, nfsd_dsr_get, nfsd_dsr_set, "%llu\n"); +/* + * /sys/kernel/debug/nfsd/io_cache_read + * + * Contents: + * %0: NFS READ will use buffered IO + * %1: NFS READ will use dontcache (buffered IO w/ dropbehind) + * %2: NFS READ will use direct IO + * + * This setting takes immediate effect for all NFS versions, + * all exports, and in all NFSD net namespaces. + */ + +static int nfsd_io_cache_read_get(void *data, u64 *val) +{ + *val = nfsd_io_cache_read; + return 0; +} + +static int nfsd_io_cache_read_set(void *data, u64 val) +{ + int ret = 0; + + switch (val) { + case NFSD_IO_BUFFERED: + nfsd_io_cache_read = NFSD_IO_BUFFERED; + break; + case NFSD_IO_DONTCACHE: + case NFSD_IO_DIRECT: + /* + * Must disable splice_read when enabling + * NFSD_IO_DONTCACHE or NFSD_IO_DIRECT. + */ + nfsd_disable_splice_read = true; + nfsd_io_cache_read = val; + break; + default: + ret = -EINVAL; + break; + } + + return ret; +} + +DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_read_fops, nfsd_io_cache_read_get, + nfsd_io_cache_read_set, "%llu\n"); + void nfsd_debugfs_exit(void) { debugfs_remove_recursive(nfsd_top_dir); @@ -44,4 +97,7 @@ void nfsd_debugfs_init(void) debugfs_create_file("disable-splice-read", S_IWUSR | S_IRUGO, nfsd_top_dir, NULL, &nfsd_dsr_fops); + + debugfs_create_file("io_cache_read", S_IWUSR | S_IRUGO, + nfsd_top_dir, NULL, &nfsd_io_cache_read_fops); } diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h index 1cd0bed57bc2f..41cb7c7feff3e 100644 --- a/fs/nfsd/nfsd.h +++ b/fs/nfsd/nfsd.h @@ -153,6 +153,15 @@ static inline void nfsd_debugfs_exit(void) {} extern bool nfsd_disable_splice_read __read_mostly; +enum { + /* Any new NFSD_IO enum value must be added at the end */ + NFSD_IO_BUFFERED, + NFSD_IO_DONTCACHE, + NFSD_IO_DIRECT, +}; + +extern u64 nfsd_io_cache_read __read_mostly; + extern int nfsd_max_blksize; static inline int nfsd_v4client(struct svc_rqst *rq) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 79439ad93880a..21441745df69a 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -49,6 +49,7 @@ #define NFSDDBG_FACILITY NFSDDBG_FILEOP bool nfsd_disable_splice_read __read_mostly; +u64 nfsd_io_cache_read __read_mostly = NFSD_IO_BUFFERED; /** * nfserrno - Map Linux errnos to NFS errnos @@ -1099,6 +1100,22 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp, size_t len; init_sync_kiocb(&kiocb, file); + + switch (nfsd_io_cache_read) { + case NFSD_IO_DIRECT: + /* Verify ondisk and memory DIO alignment */ + if (nf->nf_dio_mem_align && nf->nf_dio_read_offset_align && + (((offset | *count) & (nf->nf_dio_read_offset_align - 1)) == 0) && + (base & (nf->nf_dio_mem_align - 1)) == 0) + kiocb.ki_flags = IOCB_DIRECT; + break; + case NFSD_IO_DONTCACHE: + kiocb.ki_flags = IOCB_DONTCACHE; + break; + case NFSD_IO_BUFFERED: + break; + } + kiocb.ki_pos = offset; v = 0; -- 2.44.0