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Some drivers/filesystems need to perform additional tasks after the VMA is set up. This is typically in the form of pre-population. The forms of pre-population most likely to be performed are a PFN remap or the insertion of normal folios and PFNs into a mixed map. We start by implementing the PFN remap functionality, ensuring that we perform the appropriate actions at the appropriate time - that is setting flags at the point of .mmap_prepare, and performing the actual remap at the point at which the VMA is fully established. This prevents the driver from doing anything too crazy with a VMA at any stage, and we retain complete control over how the mm functionality is applied. Unfortunately callers still do often require some kind of custom action, so we add an optional success/error _hook to allow the caller to do something after the action has succeeded or failed. This is done at the point when the VMA has already been established, so the harm that can be done is limited. The error hook can be used to filter errors if necessary. There may be cases in which the caller absolutely must hold the file rmap lock until the operation is entirely complete. It is an edge case, but certainly the hugetlbfs mmap hook requires it. To accommodate this, we add the hide_from_rmap_until_complete flag to the mmap_action type. In this case, if a new VMA is allocated, we will hold the file rmap lock until the operation is entirely completed (including any success/error hooks). Note that we do not need to update __compat_vma_mmap() to accommodate this flag, as this function will be invoked from an .mmap handler whose VMA is not yet visible, so we implicitly hide it from the rmap. If any error arises on these final actions, we simply unmap the VMA altogether. Also update the stacked filesystem compatibility layer to utilise the action behaviour, and update the VMA tests accordingly. While we're here, rename __compat_vma_mmap_prepare() to __compat_vma_mmap() as we are now performing actions invoked by the mmap_prepare in addition to just the mmap_prepare hook. Link: https://lkml.kernel.org/r/2601199a7b2eaeadfcd8ab6e199c6d1706650c94.1760959442.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kevin Tian <kevin.tian@intel.com> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Pedro Falcato <pfalcato@suse.de> Cc: Robin Murohy <robin.murphy@arm.com> Cc: Sumanth Korikkar <sumanthk@linux.ibm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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