From e4ece59abd70d8f54e2163274dc996bb442832a6 Mon Sep 17 00:00:00 2001 From: Logan Gunthorpe Date: Thu, 10 Jun 2021 10:06:05 -0600 Subject: [PATCH] PCI/P2PDMA: Collect acs list in stack buffer to avoid sleeping 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 a smaller buffer on the stack. A 128 byte 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 cleans up the awkward (and broken) return with -ENOMEM which contradicts the return type and the caller was not prepared for. Link: https://lore.kernel.org/r/20210610160609.28447-3-logang@deltatee.com Signed-off-by: Logan Gunthorpe Signed-off-by: Bjorn Helgaas --- 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 a860137fac892..109bd73219629 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -502,11 +502,10 @@ 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); @@ -524,8 +523,6 @@ calc_map_type_and_dist_warn(struct pci_dev *provider, struct pci_dev *client, pci_name(provider)); } - kfree(acs_list.buffer); - return ret; } -- 2.30.2