This is a note to let you know that I've just added the patch titled gup: Introduce FOLL_NOFAULT flag to disable page faults to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: gup-introduce-foll_nofault-flag-to-disable-page-faults.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Fri Apr 29 11:07:48 AM CEST 2022 From: Anand Jain <anand.jain@xxxxxxxxxx> Date: Fri, 15 Apr 2022 06:28:51 +0800 Subject: gup: Introduce FOLL_NOFAULT flag to disable page faults To: stable@xxxxxxxxxxxxxxx Cc: linux-btrfs@xxxxxxxxxxxxxxx, Andreas Gruenbacher <agruenba@xxxxxxxxxx>, Anand Jain <anand.jain@xxxxxxxxxx> Message-ID: <2ee1e383ae1cca975426b54ab251257f6d4e12c0.1649951733.git.anand.jain@xxxxxxxxxx> From: Andreas Gruenbacher <agruenba@xxxxxxxxxx> commit 55b8fe703bc51200d4698596c90813453b35ae63 upstream Introduce a new FOLL_NOFAULT flag that causes get_user_pages to return -EFAULT when it would otherwise trigger a page fault. This is roughly similar to FOLL_FAST_ONLY but available on all architectures, and less fragile. Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 3 ++- mm/gup.c | 4 +++- 2 files changed, 5 insertions(+), 2 deletions(-) --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2858,7 +2858,8 @@ struct page *follow_page(struct vm_area_ #define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */ #define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO * and return without waiting upon it */ -#define FOLL_POPULATE 0x40 /* fault in page */ +#define FOLL_POPULATE 0x40 /* fault in pages (with FOLL_MLOCK) */ +#define FOLL_NOFAULT 0x80 /* do not fault in pages */ #define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */ #define FOLL_NUMA 0x200 /* force NUMA hinting page fault */ #define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */ --- a/mm/gup.c +++ b/mm/gup.c @@ -943,6 +943,8 @@ static int faultin_page(struct vm_area_s /* mlock all present pages, but do not fault in new pages */ if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) return -ENOENT; + if (*flags & FOLL_NOFAULT) + return -EFAULT; if (*flags & FOLL_WRITE) fault_flags |= FAULT_FLAG_WRITE; if (*flags & FOLL_REMOTE) @@ -2868,7 +2870,7 @@ static int internal_get_user_pages_fast( if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | FOLL_FORCE | FOLL_PIN | FOLL_GET | - FOLL_FAST_ONLY))) + FOLL_FAST_ONLY | FOLL_NOFAULT))) return -EINVAL; if (gup_flags & FOLL_PIN) Patches currently in stable-queue which might be from anand.jain@xxxxxxxxxx are queue-5.15/gup-turn-fault_in_pages_-readable-writeable-into-fault_in_-readable-writeable.patch queue-5.15/iov_iter-introduce-nofault-flag-to-disable-page-faults.patch queue-5.15/gfs2-fix-mmap-page-fault-deadlocks-for-direct-i-o.patch queue-5.15/iomap-support-partial-direct-i-o-on-user-copy-failures.patch queue-5.15/mm-gup-make-fault_in_safe_writeable-use-fixup_user_fault.patch queue-5.15/gfs2-add-wrapper-for-iomap_file_buffered_write.patch queue-5.15/gup-introduce-foll_nofault-flag-to-disable-page-faults.patch queue-5.15/iov_iter-introduce-fault_in_iov_iter_writeable.patch queue-5.15/gfs2-fix-mmap-page-fault-deadlocks-for-buffered-i-o.patch queue-5.15/btrfs-fallback-to-blocking-mode-when-doing-async-dio-over-multiple-extents.patch queue-5.15/gfs2-clean-up-function-may_grant.patch queue-5.15/btrfs-fix-deadlock-due-to-page-faults-during-direct-io-reads-and-writes.patch queue-5.15/iov_iter-turn-iov_iter_fault_in_readable-into-fault_in_iov_iter_readable.patch queue-5.15/gfs2-move-the-inode-glock-locking-to-gfs2_file_buffered_write.patch queue-5.15/gfs2-introduce-flag-for-glock-holder-auto-demotion.patch queue-5.15/iomap-fix-iomap_dio_rw-return-value-for-user-copies.patch queue-5.15/gfs2-eliminate-ip-i_gh.patch queue-5.15/iomap-add-done_before-argument-to-iomap_dio_rw.patch