linux-block.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Logan Gunthorpe <logang@deltatee.com>
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" <sbates@raithlin.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Christian König" <christian.koenig@amd.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Don Dutile" <ddutile@redhat.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Jakowski Andrzej" <andrzej.jakowski@intel.com>,
	"Minturn Dave B" <dave.b.minturn@intel.com>,
	"Jason Ekstrand" <jason@jlekstrand.net>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Xiong Jianxin" <jianxin.xiong@intel.com>,
	"Bjorn Helgaas" <helgaas@kernel.org>,
	"Ira Weiny" <ira.weiny@intel.com>,
	"Robin Murphy" <robin.murphy@arm.com>,
	"Logan Gunthorpe" <logang@deltatee.com>
Subject: [PATCH v2 02/22] PCI/P2PDMA: Use a buffer on the stack for collecting the acs list
Date: Thu, 13 May 2021 16:31:43 -0600	[thread overview]
Message-ID: <20210513223203.5542-3-logang@deltatee.com> (raw)
In-Reply-To: <20210513223203.5542-1-logang@deltatee.com>

In order to call the calc_map_type_and_dist_warn() function from
a dma_map operation, the function must not sleep. The only reason
it sleeps is to allocate memory for the seq_buf to print a verbose
warning telling the user how to disable ACS for that path.

Instead of allocating the memory with kmalloc, allocate it on
the stack with a smaller buffer. A 128B buffer is enough to print
10 pci device names. A system with 10 bridge ports between two devices
that have ACS enabled would be unusually large, so this should
still be a reasonable limit.

This also allows cleaning up the awkward (and broken) return with
-ENOMEM which contradicts the return type and the caller was
not prepared for.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 drivers/pci/p2pdma.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 6f90e9812f6e..3a5fb63c5f2c 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -500,11 +500,10 @@ calc_map_type_and_dist_warn(struct pci_dev *provider, struct pci_dev *client,
 {
 	struct seq_buf acs_list;
 	bool acs_redirects;
+	char buf[128];
 	int ret;
 
-	seq_buf_init(&acs_list, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE);
-	if (!acs_list.buffer)
-		return -ENOMEM;
+	seq_buf_init(&acs_list, buf, sizeof(buf));
 
 	ret = calc_map_type_and_dist(provider, client, dist, &acs_redirects,
 				     &acs_list);
@@ -522,8 +521,6 @@ calc_map_type_and_dist_warn(struct pci_dev *provider, struct pci_dev *client,
 			 pci_name(provider));
 	}
 
-	kfree(acs_list.buffer);
-
 	return ret;
 }
 
-- 
2.20.1


  parent reply	other threads:[~2021-05-13 22:32 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-13 22:31 [PATCH v2 00/22] Add new DMA mapping operation for P2PDMA Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 01/22] PCI/P2PDMA: Rename upstream_bridge_distance() and rework documentation Logan Gunthorpe
2021-05-13 22:31 ` Logan Gunthorpe [this message]
2021-05-13 22:31 ` [PATCH v2 03/22] PCI/P2PDMA: Cleanup type for return value of calc_map_type_and_dist() Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 04/22] PCI/P2PDMA: Avoid pci_get_slot() which sleeps Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 05/22] PCI/P2PDMA: Print a warning if the host bridge is not in the whitelist Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 06/22] PCI/P2PDMA: Attempt to set map_type if it has not been set Logan Gunthorpe
2021-05-14 13:49   ` Christoph Hellwig
2021-05-14 16:15     ` Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 07/22] PCI/P2PDMA: Refactor pci_p2pdma_map_type() to take pagemap and device Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 08/22] dma-mapping: Allow map_sg() ops to return negative error codes Logan Gunthorpe
2021-05-14 13:51   ` Christoph Hellwig
2021-05-14 16:15     ` Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 09/22] dma-direct: Return appropriate error code from dma_direct_map_sg() Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 10/22] iommu: Return full error code from iommu_map_sg[_atomic]() Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 11/22] dma-iommu: Return error code from iommu_dma_map_sg() Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 12/22] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 13/22] PCI/P2PDMA: Make pci_p2pdma_map_type() non-static Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 14/22] PCI/P2PDMA: Introduce helpers for dma_map_sg implementations Logan Gunthorpe
2021-05-14 13:53   ` Christoph Hellwig
2021-05-14 16:16     ` Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 15/22] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg Logan Gunthorpe
2021-05-14 13:57   ` Christoph Hellwig
2021-05-14 16:17     ` Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 16/22] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 17/22] iommu/dma: Support PCI P2PDMA pages in dma-iommu map_sg Logan Gunthorpe
2021-05-13 22:31 ` [PATCH v2 18/22] nvme-pci: Check DMA ops when indicating support for PCI P2PDMA Logan Gunthorpe
2021-05-13 22:32 ` [PATCH v2 19/22] nvme-pci: Convert to using dma_map_sgtable() Logan Gunthorpe
2021-05-13 22:32 ` [PATCH v2 20/22] RDMA/core: Introduce ib_dma_pci_p2p_dma_supported() Logan Gunthorpe
2021-05-13 22:32 ` [PATCH v2 21/22] RDMA/rw: use dma_map_sgtable() Logan Gunthorpe
2021-05-13 22:32 ` [PATCH v2 22/22] PCI/P2PDMA: Remove pci_p2pdma_[un]map_sg() Logan Gunthorpe
2021-05-14 14:00 ` [PATCH v2 00/22] Add new DMA mapping operation for P2PDMA Christoph Hellwig
2021-05-14 16:30   ` Logan Gunthorpe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210513223203.5542-3-logang@deltatee.com \
    --to=logang@deltatee.com \
    --cc=andrzej.jakowski@intel.com \
    --cc=christian.koenig@amd.com \
    --cc=dan.j.williams@intel.com \
    --cc=daniel.vetter@ffwll.ch \
    --cc=dave.b.minturn@intel.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=ddutile@redhat.com \
    --cc=hch@lst.de \
    --cc=helgaas@kernel.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=ira.weiny@intel.com \
    --cc=jason@jlekstrand.net \
    --cc=jgg@ziepe.ca \
    --cc=jhubbard@nvidia.com \
    --cc=jianxin.xiong@intel.com \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-nvme@lists.infradead.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=sbates@raithlin.com \
    --cc=willy@infradead.org \
    --subject='Re: [PATCH v2 02/22] PCI/P2PDMA: Use a buffer on the stack for collecting the acs list' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).