Hi Leon, Please see below...
On Wed, 15 Jul 2026 18:47:24 +0100 Matt Evans <[email protected]> wrote: > Preparing for a refactor in a subsequent patch, split the pool-related > release code into a new pci_p2pdma_release_pool() function. > > This allows future compile-time selection of a null implementation for > pci_p2pdma_release_pool(), when p2pdma.c is refactored into core- and > P2P-related files. > > Signed-off-by: Matt Evans <[email protected]> > Acked-by: Bjorn Helgaas <[email protected]> > Reviewed-by: Logan Gunthorpe <[email protected]> > --- > drivers/pci/p2pdma.c | 24 ++++++++++++++---------- > 1 file changed, 14 insertions(+), 10 deletions(-) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index b2d5266f8653..498bca257419 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -226,6 +226,17 @@ static const struct dev_pagemap_ops p2pdma_pgmap_ops = { > .folio_free = p2pdma_folio_free, > }; > > +static void pci_p2pdma_release_pool(struct pci_dev *pdev, > + struct pci_p2pdma *p2pdma) > +{ > + if (!p2pdma->pool) > + return; > + > + synchronize_rcu(); Sashiko notes[1] a high, preexisting issue here that looks like it was introduced via 372d6d1b8ae3 ("PCI/P2PDMA: Refactor to separate core P2P functionality from memory allocation"). That commit creates a two-tier scheme where the optional memory allocation capabilities, such as the pool, live above a core layer. Prior to that commit, this synchronize RCU call was unconditional. Making it conditional on the pool suggests it was only considered relevant to the optional layer. However, map_types, which remains in the core layer, is RCU referenced. Was the synchronize_rcu() call here miscategorized into the optional tier? Should it instead have remained unconditional? We might need a precursor Fixes: patch to this series that makes it unconditional in pci_p2pdma_release(), so that it remains there with this refactor rather than becoming part of this new pool release function. Thanks, Alex [1]https://lore.kernel.org/all/[email protected]/ > + gen_pool_destroy(p2pdma->pool); > + sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group); > +} > + > static void pci_p2pdma_release(void *data) > { > struct pci_dev *pdev = data; > @@ -237,15 +248,8 @@ static void pci_p2pdma_release(void *data) > > /* Flush and disable pci_alloc_p2p_mem() */ > pdev->p2pdma = NULL; > - if (p2pdma->pool) > - synchronize_rcu(); > + pci_p2pdma_release_pool(pdev, p2pdma); > xa_destroy(&p2pdma->map_types); > - > - if (!p2pdma->pool) > - return; > - > - gen_pool_destroy(p2pdma->pool); > - sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group); > } > > /** > @@ -946,8 +950,8 @@ void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size) > struct pci_p2pdma *p2pdma; > > /* > - * Pairs with synchronize_rcu() in pci_p2pdma_release() to > - * ensure pdev->p2pdma is non-NULL for the duration of the > + * Pairs with synchronize_rcu() in pci_p2pdma_release_pool() > + * to ensure pdev->p2pdma is non-NULL for the duration of the > * read-lock. > */ > rcu_read_lock();
