From patchwork Fri Oct 22 19:02:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 12578531 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB5A6C433EF for ; Fri, 22 Oct 2021 19:02:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7CBC61038 for ; Fri, 22 Oct 2021 19:02:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234030AbhJVTFB (ORCPT ); Fri, 22 Oct 2021 15:05:01 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:36262 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233973AbhJVTEw (ORCPT ); Fri, 22 Oct 2021 15:04:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634929354; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rbeUDRvfOB2aZ1sHCO5D2RGmW9kgUvKEDFff366LXY4=; b=SQuAigKCeqzq6mykdvuplYVrRLovuFy0uwWgtuT+vek8IjH3BRXehefg5oaZnRj+W8Lgu2 ZCwt/MQ5WjoE0SCXKKRn4XYyfycm2L7cewotVR1f3ISinIyVIgyZlFwZYbt+/BE9/vZnp0 z+NCgqOVxYZ/hVxoQiKspXL0tU2yXOA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-456-GJhCiyf0PZGta_LRvW2QGg-1; Fri, 22 Oct 2021 15:02:28 -0400 X-MC-Unique: GJhCiyf0PZGta_LRvW2QGg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 230C1806688; Fri, 22 Oct 2021 19:02:26 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id EBBDE5C1A3; Fri, 22 Oct 2021 19:02:22 +0000 (UTC) Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH v2 13/53] fscache: Implement volume-level access helpers From: David Howells To: linux-cachefs@redhat.com Cc: dhowells@redhat.com, Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , Jeff Layton , Matthew Wilcox , Alexander Viro , Omar Sandoval , Linus Torvalds , linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 22 Oct 2021 20:02:22 +0100 Message-ID: <163492934215.1038219.4516739049966201721.stgit@warthog.procyon.org.uk> In-Reply-To: <163492911924.1038219.13107463173777870713.stgit@warthog.procyon.org.uk> References: <163492911924.1038219.13107463173777870713.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org Add a pair of helper functions to manage access to a volume, pinning the volume in place for the duration to prevent cache withdrawal from removing it: bool fscache_begin_volume_access(struct fscache_volume *volume, enum fscache_access_trace why); void fscache_end_volume_access(struct fscache_volume *volume, enum fscache_access_trace why); The first is intended for internal use only, but the second will be used by the cache backend also. Signed-off-by: David Howells cc: linux-cachefs@redhat.com --- fs/fscache/internal.h | 2 ++ fs/fscache/main.c | 1 + fs/fscache/volume.c | 47 ++++++++++++++++++++++++++++++++++++++++ include/linux/fscache-cache.h | 3 +++ include/trace/events/fscache.h | 30 ++++++++++++++++++++++++++ 5 files changed, 83 insertions(+) diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h index 5546c24d18d8..18f9a408a4f4 100644 --- a/fs/fscache/internal.h +++ b/fs/fscache/internal.h @@ -107,6 +107,8 @@ struct fscache_volume *fscache_get_volume(struct fscache_volume *volume, enum fscache_volume_trace where); void fscache_put_volume(struct fscache_volume *volume, enum fscache_volume_trace where); +bool fscache_begin_volume_access(struct fscache_volume *volume, + enum fscache_access_trace why); void fscache_create_volume(struct fscache_volume *volume, bool wait); diff --git a/fs/fscache/main.c b/fs/fscache/main.c index e1f14b29cff4..6a024c45eb0b 100644 --- a/fs/fscache/main.c +++ b/fs/fscache/main.c @@ -22,6 +22,7 @@ MODULE_PARM_DESC(fscache_debug, "FS-Cache debugging mask"); EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache); +EXPORT_TRACEPOINT_SYMBOL(fscache_access_volume); struct workqueue_struct *fscache_wq; EXPORT_SYMBOL(fscache_wq); diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c index 924851888f18..d539d6ec2664 100644 --- a/fs/fscache/volume.c +++ b/fs/fscache/volume.c @@ -33,6 +33,53 @@ static void fscache_see_volume(struct fscache_volume *volume, trace_fscache_volume(volume->debug_id, ref, where); } +/* + * Pin the cache behind a volume so that we can access it. + */ +static void __fscache_begin_volume_access(struct fscache_volume *volume, + enum fscache_access_trace why) +{ + int n_accesses; + + n_accesses = atomic_inc_return(&volume->n_accesses); + smp_mb__after_atomic(); + trace_fscache_access_volume(volume->debug_id, refcount_read(&volume->ref), + n_accesses, why); +} + +/* + * If the cache behind a volume is live, pin it so that we can access it. + */ +bool fscache_begin_volume_access(struct fscache_volume *volume, + enum fscache_access_trace why) +{ + if (!fscache_cache_is_live(volume->cache)) + return false; + __fscache_begin_volume_access(volume, why); + if (!fscache_cache_is_live(volume->cache)) { + fscache_end_volume_access(volume, fscache_access_unlive); + return false; + } + return true; +} + +/* + * Mark the end of an access on a volume. + */ +void fscache_end_volume_access(struct fscache_volume *volume, + enum fscache_access_trace why) +{ + int n_accesses; + + smp_mb__before_atomic(); + n_accesses = atomic_dec_return(&volume->n_accesses); + trace_fscache_access_volume(volume->debug_id, refcount_read(&volume->ref), + n_accesses, why); + if (n_accesses == 0) + wake_up_var(&volume->n_accesses); +} +EXPORT_SYMBOL(fscache_end_volume_access); + static long fscache_compare_volume(const struct fscache_volume *a, const struct fscache_volume *b) { diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h index e075cca1a30d..7db4dda74951 100644 --- a/include/linux/fscache-cache.h +++ b/include/linux/fscache-cache.h @@ -77,6 +77,9 @@ extern struct fscache_cache *fscache_acquire_cache(const char *name); extern void fscache_put_cache(struct fscache_cache *cache, enum fscache_cache_trace where); +extern void fscache_end_volume_access(struct fscache_volume *volume, + enum fscache_access_trace why); + extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie, enum fscache_cookie_trace where); extern void fscache_put_cookie(struct fscache_cookie *cookie, diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h index d09d7e3ac86c..4b35fe9cd906 100644 --- a/include/trace/events/fscache.h +++ b/include/trace/events/fscache.h @@ -40,6 +40,7 @@ enum fscache_volume_trace { fscache_volume_put_relinquish, fscache_volume_see_create_work, fscache_volume_see_hash_wake, + fscache_volume_wait_create_work, }; enum fscache_cookie_trace { @@ -239,6 +240,35 @@ TRACE_EVENT(fscache_access_cache, __entry->n_accesses) ); +TRACE_EVENT(fscache_access_volume, + TP_PROTO(unsigned int volume_debug_id, + int ref, + int n_accesses, + enum fscache_access_trace why), + + TP_ARGS(volume_debug_id, ref, n_accesses, why), + + TP_STRUCT__entry( + __field(unsigned int, volume ) + __field(int, ref ) + __field(int, n_accesses ) + __field(enum fscache_access_trace, why ) + ), + + TP_fast_assign( + __entry->volume = volume_debug_id; + __entry->ref = ref; + __entry->n_accesses = n_accesses; + __entry->why = why; + ), + + TP_printk("V=%08x %s r=%d a=%d", + __entry->volume, + __print_symbolic(__entry->why, fscache_access_traces), + __entry->ref, + __entry->n_accesses) + ); + TRACE_EVENT(fscache_acquire, TP_PROTO(struct fscache_cookie *cookie),