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s=20200525; h=Subject:MIME-Version:References:In-Reply-To: Message-Id:Date:Cc:To:From:content-disposition; bh=M9URDKLIjWjYTVDR2jo0iTH/7oGIDWR/L4jsn5dDFEQ=; b=n061DgFCU9NzN4lKQkcvE0Vgff KqhQDsQf0FiHKJh0lpMDW4cqOXRvLM/1rmcyvnVpn/5jOAJSiT/yAzjgyESNl4ZXz+x7ORPlwQVjh SSm0Re7Hp1abk1zwbYETKG6X5/K7JsNKOCnjUK3UmCvlBxfkfTH+qwQbextk6lh11y0h6q58XSIQw 6gOm0v5wVAy8/07ejEh5EqIUurPNcs1vtn25yGx05VbRETmh+h2ex+rOAzXUDibvFm2ryrZdrgWkq YeZI+qDF6xJDuqpnUx1/jIX8Tvr5C7DvFVIDvpZsoLK6/v3ulzBnPocYSJspfOD6XijvgJtl+IlbT GAESFp5w==; Received: from cgy1-donard.priv.deltatee.com ([172.16.1.31]) by ale.deltatee.com with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lhJsL-0000nF-QQ; Thu, 13 May 2021 16:32:15 -0600 Received: from gunthorp by cgy1-donard.priv.deltatee.com with local (Exim 4.92) (envelope-from ) id 1lhJsG-0001Se-6p; Thu, 13 May 2021 16:32:08 -0600 From: Logan Gunthorpe To: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org Cc: Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , =?UTF-8?q?Christian=20K=C3=B6nig?= , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy , Logan Gunthorpe Date: Thu, 13 May 2021 16:31:45 -0600 Message-Id: <20210513223203.5542-5-logang@deltatee.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210513223203.5542-1-logang@deltatee.com> References: <20210513223203.5542-1-logang@deltatee.com> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 172.16.1.31 X-SA-Exim-Rcpt-To: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, sbates@raithlin.com, hch@lst.de, jgg@ziepe.ca, christian.koenig@amd.com, jhubbard@nvidia.com, ddutile@redhat.com, willy@infradead.org, daniel.vetter@ffwll.ch, jason@jlekstrand.net, dave.hansen@linux.intel.com, helgaas@kernel.org, dan.j.williams@intel.com, andrzej.jakowski@intel.com, dave.b.minturn@intel.com, jianxin.xiong@intel.com, ira.weiny@intel.com, robin.murphy@arm.com, logang@deltatee.com X-SA-Exim-Mail-From: gunthorp@deltatee.com Subject: [PATCH v2 04/22] PCI/P2PDMA: Avoid pci_get_slot() which sleeps X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=deltatee.com header.s=20200525 header.b=n061DgFC; dmarc=none; spf=pass (imf18.hostedemail.com: domain of gunthorp@deltatee.com designates 204.191.154.188 as permitted sender) smtp.mailfrom=gunthorp@deltatee.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8C4982000260 X-Stat-Signature: k4rz6xj9ggcufwxsrydfhnaswn1e5ka3 X-HE-Tag: 1620945139-205709 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: In order to use upstream_bridge_distance_warn() from a dma_map function, it must not sleep. However, pci_get_slot() takes the pci_bus_sem so it might sleep. In order to avoid this, try to get the host bridge's device from the firs= t element in the device list. It should be impossible for the host bridge's device to go away while references are held on child devices, so the firs= t element should not be able to change and, thus, this should be safe. Introduce a static function called pci_host_bridge_dev() to obtain the host bridge's root device. Signed-off-by: Logan Gunthorpe --- drivers/pci/p2pdma.c | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 09c864f193d2..175da3a9c8fb 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -308,10 +308,41 @@ static const struct pci_p2pdma_whitelist_entry { {} }; =20 +/* + * This lookup function tries to find the PCI device corresponding to a = given + * host bridge. + * + * It assumes the host bridge device is the first PCI device in the + * bus->devices list and that the devfn is 00.0. These assumptions shoul= d hold + * for all the devices in the whitelist above. + * + * This function is equivalent to pci_get_slot(host->bus, 0), however it= does + * not take the pci_bus_sem lock seeing __host_bridge_whitelist() must n= ot + * sleep. + * + * For this to be safe, the caller should hold a reference to a device o= n the + * bridge, which should ensure the host_bridge device will not be freed + * or removed from the head of the devices list. + */ +static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host) +{ + struct pci_dev *root; + + root =3D list_first_entry_or_null(&host->bus->devices, + struct pci_dev, bus_list); + + if (!root) + return NULL; + if (root->devfn !=3D PCI_DEVFN(0, 0)) + return NULL; + + return root; +} + static bool __host_bridge_whitelist(struct pci_host_bridge *host, bool same_host_bridge) { - struct pci_dev *root =3D pci_get_slot(host->bus, PCI_DEVFN(0, 0)); + struct pci_dev *root =3D pci_host_bridge_dev(host); const struct pci_p2pdma_whitelist_entry *entry; unsigned short vendor, device; =20 @@ -320,7 +351,6 @@ static bool __host_bridge_whitelist(struct pci_host_b= ridge *host, =20 vendor =3D root->vendor; device =3D root->device; - pci_dev_put(root); =20 for (entry =3D pci_p2pdma_whitelist; entry->vendor; entry++) { if (vendor !=3D entry->vendor || device !=3D entry->device) --=20 2.20.1