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Howlett" , Nikita Kalyazin , Michal Hocko , David Hildenbrand , Andrea Arcangeli , Oscar Salvador , Axel Rasmussen , Ujwal Kundur Subject: [PATCH v2 2/4] mm/shmem: Support vm_uffd_ops API Date: Fri, 27 Jun 2025 11:46:53 -0400 Message-ID: <20250627154655.2085903-3-peterx@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250627154655.2085903-1-peterx@redhat.com> References: <20250627154655.2085903-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xXKvNT5aRwqtwneFu-zzJ5t22F9OO-OznApV_X1EeQc_1751039225 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4A8D340003 X-Stat-Signature: 4bzeqo5zt1d8uec9hofzksmjzaj7z7gk X-Rspam-User: X-HE-Tag: 1751039227-410149 X-HE-Meta: U2FsdGVkX1+Y1/LjolFI2QF0SGW7RKVCt2eWOsFcnXole8HoyXRL2DNxMYUPNds4StFymveftDSeNGaMjX3Gul5zsMv94L2Vg6UidO9OPFL+L4R5gIYixLNFKKynetsS/rLbj+3jNeDvCsUVyK8aPGwnUDKLpifXXtK7fFrW071ZMwk2SBnYelblaFERdCZG3kZuB3lEKKDfPc51LcVkVDeCSAtKjvSVa95GmUmaoTVZ88il8+3mfJi7hbFJtxANMUl0VGU/vK4Kd01YMGBehjtB055bi86Pv1cQN1/5xAOMoHShEFoLAKcnf3muP6Io7mFSCRdBqfNuQHNkG3OB8Pv3Ibk1Uvg554kLh2GrZayPmbpumnNQrZaadELcVda7K7rU4gPfKjxNwDyz7Y1YVqwBQiQSO3vUUv3nHqLWRwn7CoDbziTqZCQqUnsUm3MftRw/5b+ozoHWQG5TSctiKx2oQSOoQN0c+zmgTSxz32x4QGoPy5MAUIKDqmXM03VGnlikk1zdTmdJ7rItb1R/yund34H2YiZMESnFCyk71EMFMHV+iVyGB4fQSX1/v46hPT0zW+WZVgQq3Hj0Dk59DifUN/dcj25TyOnP4SvddDNiWKYbFEKfnsPso3lTwVkCeHx8apC6Q/TdVGzlLX8ZHZo545JGuZQVD8qtmsnWkKU60G4faqECyyiPeOrqJMPJx39FqWRCkN5ONEN0hj2A2tudmPcnK5EKY7rCtVnIvDTXoZ6eqH58KhoIIejVbk1aAl5IF3OEzPpt5MmERu5rQ/2khpbi1TOHW3/lhYfk6LBKpUFHSGpKsKqOhAFijsHBh1Y+DyWZoOHYL1ZH6gMGt3Hl6WxryoPTe1Wy3tnYRdlOSnpv8Zh+X4UQXxcInF6fvDbxjgh1ALokAK3mwxobtGwYZYZcfl2uviPPF6Z3XClmGVohFABmD3ZfPXYSlYtqQbBIVE/UUwN0U+l72kX wuEPUnA8 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 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: List-Subscribe: List-Unsubscribe: Add support for the new vm_uffd_ops API for shmem. Note that this only introduces the support, the API is not yet used by core mm. Due to the tailored uffd_copy() API, shmem is extremely easy to support it by reusing the existing mfill function. It only needs a separate uffd_get_folio() definition but that's oneliner. Cc: Hugh Dickins Signed-off-by: Peter Xu --- mm/shmem.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index 2b19965d27df..9a8b8dd4709b 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3151,6 +3151,13 @@ static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap, #endif /* CONFIG_TMPFS_QUOTA */ #ifdef CONFIG_USERFAULTFD + +static int shmem_uffd_get_folio(struct inode *inode, pgoff_t pgoff, + struct folio **folio) +{ + return shmem_get_folio(inode, pgoff, 0, folio, SGP_NOALLOC); +} + int shmem_mfill_atomic_pte(pmd_t *dst_pmd, struct vm_area_struct *dst_vma, unsigned long dst_addr, @@ -5194,6 +5201,19 @@ static int shmem_error_remove_folio(struct address_space *mapping, return 0; } +#ifdef CONFIG_USERFAULTFD +static const vm_uffd_ops shmem_uffd_ops = { + .uffd_features = __VM_UFFD_FLAGS, + .uffd_ioctls = BIT(_UFFDIO_COPY) | + BIT(_UFFDIO_ZEROPAGE) | + BIT(_UFFDIO_WRITEPROTECT) | + BIT(_UFFDIO_CONTINUE) | + BIT(_UFFDIO_POISON), + .uffd_get_folio = shmem_uffd_get_folio, + .uffd_copy = shmem_mfill_atomic_pte, +}; +#endif + static const struct address_space_operations shmem_aops = { .dirty_folio = noop_dirty_folio, #ifdef CONFIG_TMPFS @@ -5296,6 +5316,9 @@ static const struct vm_operations_struct shmem_vm_ops = { .set_policy = shmem_set_policy, .get_policy = shmem_get_policy, #endif +#ifdef CONFIG_USERFAULTFD + .userfaultfd_ops = &shmem_uffd_ops, +#endif }; static const struct vm_operations_struct shmem_anon_vm_ops = { @@ -5305,6 +5328,9 @@ static const struct vm_operations_struct shmem_anon_vm_ops = { .set_policy = shmem_set_policy, .get_policy = shmem_get_policy, #endif +#ifdef CONFIG_USERFAULTFD + .userfaultfd_ops = &shmem_uffd_ops, +#endif }; int shmem_init_fs_context(struct fs_context *fc) -- 2.49.0