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Prakash Sangappa 2d6d6f5a09 mm: userfaultfd: add feature to request for a signal delivery 
In some cases, userfaultfd mechanism should just deliver a SIGBUS signal
to the faulting process, instead of the page-fault event.  Dealing with
page-fault event using a monitor thread can be an overhead in these
cases.  For example applications like the database could use the
signaling mechanism for robustness purpose.

Database uses hugetlbfs for performance reason.  Files on hugetlbfs
filesystem are created and huge pages allocated using fallocate() API.
Pages are deallocated/freed using fallocate() hole punching support.
These files are mmapped and accessed by many processes as shared memory.
The database keeps track of which offsets in the hugetlbfs file have
pages allocated.

Any access to mapped address over holes in the file, which can occur due
to bugs in the application, is considered invalid and expect the process
to simply receive a SIGBUS.  However, currently when a hole in the file
is accessed via the mapped address, kernel/mm attempts to automatically
allocate a page at page fault time, resulting in implicitly filling the
hole in the file.  This may not be the desired behavior for applications
like the database that want to explicitly manage page allocations of
hugetlbfs files.

Using userfaultfd mechanism with this support to get a signal, database
application can prevent pages from being allocated implicitly when
processes access mapped address over holes in the file.

This patch adds UFFD_FEATURE_SIGBUS feature to userfaultfd mechnism to
request for a SIGBUS signal.

See following for previous discussion about the database requirement
leading to this proposal as suggested by Andrea.

http://www.spinics.net/lists/linux-mm/msg129224.html

Link: http://lkml.kernel.org/r/1501552446-748335-2-git-send-email-prakash.sangappa@oracle.com
Signed-off-by: Prakash Sangappa <prakash.sangappa@oracle.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2017-09-06 17:27:29 -07:00
..
9p fscache: remove unused ->now_uncached callback 2017-09-06 17:27:26 -07:00
adfs
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affs affs: Implement show_options 2017-07-11 06:06:17 -04:00
afs fscache: remove unused ->now_uncached callback 2017-09-06 17:27:26 -07:00
autofs4 Fix up over-eager 'wait_queue_t' renaming 2017-07-10 11:40:19 -07:00
befs Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
bfs bfs: fix sanity checks for empty files 2017-07-12 16:26:00 -07:00
btrfs Btrfs: fix blk_status_t/errno confusion 2017-08-24 17:19:02 +02:00
cachefiles sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming 2017-06-20 12:19:14 +02:00
ceph fscache: remove unused ->now_uncached callback 2017-09-06 17:27:26 -07:00
cifs fscache: remove unused ->now_uncached callback 2017-09-06 17:27:26 -07:00
coda fs: implement vfs_iter_write using do_iter_write 2017-06-29 17:49:23 -04:00
configfs configfs: Introduce config_item_get_unless_zero() 2017-06-12 13:20:20 +02:00
cramfs
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crypto The first major feature for ext4 this merge window is the largedir 2017-07-09 09:31:22 -07:00
debugfs Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
devpts pty: Repair TIOCGPTPEER 2017-08-24 13:23:03 -07:00
dlm net: Work around lockdep limitation in sockets that use sockets 2017-03-09 18:23:27 -08:00
ecryptfs ecryptfs: Convert to separately allocated bdi 2017-04-20 12:09:55 -06:00
efivarfs VFS: Kill off s_options and helpers 2017-07-11 06:09:21 -04:00
efs
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exofs mm: drop "wait" parameter from write_one_page() 2017-07-05 18:44:22 -04:00
exportfs Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-03-03 11:38:56 -08:00
ext2 dax: use common 4k zero page for dax mmap reads 2017-09-06 17:27:24 -07:00
ext4 mm: remove nr_pages argument from pagevec_lookup{,_range}() 2017-09-06 17:27:27 -07:00
f2fs f2fs: avoid cpu lockup 2017-07-17 19:23:18 -07:00
fat fat: fix using uninitialized fields of fat_inode/fsinfo_inode 2017-03-09 17:01:10 -08:00
freevxfs
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fscache mm: remove nr_pages argument from pagevec_lookup{,_range}() 2017-09-06 17:27:27 -07:00
fuse Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse 2017-08-11 11:20:48 -07:00
gfs2 Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
hfs fs: semove set but not checked AOP_FLAG_UNINTERRUPTIBLE flag 2017-05-08 17:15:14 -07:00
hfsplus hfsplus: Don't clear SGID when inheriting ACLs 2017-07-18 18:23:39 +02:00
hostfs
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hpfs sched/headers: Prepare to move signal wakeup & sigpending methods from <linux/sched.h> into <linux/sched/signal.h> 2017-03-02 08:42:32 +01:00
hugetlbfs mm: remove nr_pages argument from pagevec_lookup{,_range}() 2017-09-06 17:27:27 -07:00
isofs isofs: Fix off-by-one in 'session' mount option parsing 2017-07-18 12:33:16 +02:00
jbd2 Writeback error handling fixes (pile #2) 2017-07-07 19:38:17 -07:00
jffs2 jffs2: fix spelling mistake: "requestied" -> "requested" 2017-04-19 11:35:55 -07:00
jfs jfs should use MAX_LFS_FILESIZE when calculating s_maxbytes 2017-08-31 17:02:21 -07:00
kernfs kernfs: Clarify lockdep name for kn->count 2017-08-28 16:50:15 +02:00
lockd sunrpc: mark all struct svc_version instances as const 2017-07-13 15:58:03 -04:00
minix Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-08 10:50:54 -07:00
ncpfs mm: per-cgroup memory reclaim stats 2017-07-06 16:24:35 -07:00
nfs fscache: remove unused ->now_uncached callback 2017-09-06 17:27:26 -07:00
nfs_common
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nfsd annotate RWF_... flags 2017-08-31 17:32:38 -04:00
nilfs2 mm: remove nr_pages argument from pagevec_lookup{,_range}() 2017-09-06 17:27:27 -07:00
nls
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notify dentry name snapshots 2017-07-07 20:09:10 -04:00
ntfs ntfs: Use ERR_CAST() to avoid cross-structure cast 2017-05-28 10:11:48 -07:00
ocfs2 ocfs2: clean up some dead code 2017-09-06 17:27:24 -07:00
omfs omfs: Implement show_options 2017-07-06 03:31:46 -04:00
openpromfs
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orangefs Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
overlayfs overlayfs, locking: Remove smp_mb__before_spinlock() usage 2017-08-10 12:29:02 +02:00
proc mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -07:00
pstore Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
qnx4
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qnx6
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quota quota: correct space limit check 2017-08-07 16:51:28 +02:00
ramfs mm: make pagevec_lookup() update index 2017-09-06 17:27:26 -07:00
reiserfs reiserfs: preserve i_mode if __reiserfs_set_acl() fails 2017-07-18 11:24:08 +02:00
romfs
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squashfs fs/pstore: fs/squashfs: change usage of LZ4 to work with new LZ4 version 2017-02-24 17:46:57 -08:00
sysfs sysfs: be careful of error returns from ops->show() 2017-04-08 17:33:32 +02:00
sysv mm: drop "wait" parameter from write_one_page() 2017-07-05 18:44:22 -04:00
tracefs VFS: Don't use save/replace_mount_options if not using generic_show_options 2017-07-06 03:31:46 -04:00
ubifs ubifs: Set double hash cookie also for RENAME_EXCHANGE 2017-07-14 22:50:57 +02:00
udf udf: Convert udf_disk_stamp_to_time() to use mktime64() 2017-06-14 11:21:02 +02:00
ufs Writeback error handling fixes (pile #1) 2017-07-07 18:39:15 -07:00
xfs dax: use common 4k zero page for dax mmap reads 2017-09-06 17:27:24 -07:00
Kconfig fs/Kconfig: kill CONFIG_PERCPU_RWSEM some more 2017-07-12 16:26:00 -07:00
Kconfig.binfmt
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Makefile
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aio.c fs: add O_DIRECT and aio support for sending down write life time hints 2017-06-27 12:05:36 -06:00
anon_inodes.c
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attr.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h> 2017-03-02 08:42:29 +01:00
bad_inode.c statx: Add a system call to make enhanced file info available 2017-03-02 20:51:15 -05:00
binfmt_aout.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h> 2017-03-02 08:42:36 +01:00
binfmt_elf.c x86/elf: Remove the unnecessary ADDR_NO_RANDOMIZE checks 2017-08-16 20:32:02 +02:00
binfmt_elf_fdpic.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
binfmt_em86.c
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binfmt_flat.c binfmt_flat: Use %u to format u32 2017-07-16 09:24:05 -07:00
binfmt_misc.c fs: constify tree_descr arrays passed to simple_fill_super() 2017-04-26 23:54:06 -04:00
binfmt_script.c
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block_dev.c Writeback error handling fixes (pile #2) 2017-07-07 19:38:17 -07:00
buffer.c mm: remove nr_pages argument from pagevec_lookup{,_range}() 2017-09-06 17:27:27 -07:00
char_dev.c char_dev: order /proc/devices by major number 2017-07-17 15:28:50 +02:00
compat.c fs/compat.c: trim unused includes 2017-04-17 12:52:27 -04:00
compat_binfmt_elf.c
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compat_ioctl.c Merge branch 'work.__copy_in_user' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-08 10:15:02 -07:00
coredump.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h> 2017-03-02 08:42:36 +01:00
dax.c dax: initialize variable pfn before using it 2017-09-06 17:27:24 -07:00
dcache.c Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
dcookies.c
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direct-io.c fs: add O_DIRECT and aio support for sending down write life time hints 2017-06-27 12:05:36 -06:00
drop_caches.c
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eventfd.c There has been a fair amount of activity in the docs tree this time 2017-07-03 21:13:25 -07:00
eventpoll.c epoll: fix race between ep_poll_callback(POLLFREE) and ep_free()/ep_remove() 2017-09-01 13:07:35 -07:00
exec.c exec: Limit arg stack to at most 75% of _STK_LIM 2017-07-07 20:05:08 -07:00
fcntl.c vfs: fix flock compat thinko 2017-07-07 13:48:18 -07:00
fhandle.c fhandle: move compat syscalls from compat.c 2017-04-17 12:52:26 -04:00
file.c fs/file.c: replace alloc_fdmem() with kvmalloc() alternative 2017-07-06 16:24:30 -07:00
file_table.c fs: new infrastructure for writeback error handling and reporting 2017-07-06 07:02:25 -04:00
filesystems.c Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
fs-writeback.c writeback: rework wb_[dec|inc]_stat family of functions 2017-07-12 16:26:05 -07:00
fs_pin.c sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming 2017-06-20 12:19:14 +02:00
fs_struct.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
inode.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-08 10:50:54 -07:00
internal.h Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-05-09 09:12:53 -07:00
ioctl.c sched/headers: Prepare for the reduction of <linux/sched.h>'s signal API dependency 2017-03-02 08:42:37 +01:00
iomap.c iomap: fix integer truncation issues in the zeroing and dirtying helpers 2017-08-11 16:56:33 -07:00
libfs.c fs: convert __generic_file_fsync to use errseq_t based reporting 2017-07-06 07:02:29 -04:00
locks.c fs/locks: pass kernel struct flock to fcntl_getlk/setlk 2017-05-27 06:07:19 -04:00
mbcache.c ext4: xattr inode deduplication 2017-06-22 11:44:55 -04:00
mount.h Now that IPC and other changes have landed, enable manual markings for 2017-07-19 08:55:18 -07:00
mpage.c There has been a fair amount of activity in the docs tree this time 2017-07-03 21:13:25 -07:00
namei.c Now that IPC and other changes have landed, enable manual markings for 2017-07-19 08:55:18 -07:00
namespace.c Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
no-block.c
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nsfs.c VFS: Provide empty name qstr 2017-07-06 03:27:09 -04:00
open.c Writeback error handling fixes (pile #2) 2017-07-07 19:38:17 -07:00
pipe.c VFS: Provide empty name qstr 2017-07-06 03:27:09 -04:00
pnode.c mnt: Make propagate_umount less slow for overlapping mount propagation trees 2017-05-23 08:41:17 -05:00
pnode.h
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posix_acl.c sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h> 2017-03-02 08:42:31 +01:00
proc_namespace.c sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
read_write.c annotate RWF_... flags 2017-08-31 17:32:38 -04:00
readdir.c readdir: move compat syscalls from compat.c 2017-04-17 12:52:24 -04:00
select.c fs/select: Fix memory corruption in compat_get_fd_set() 2017-08-28 16:09:19 -07:00
seq_file.c mm: introduce kv[mz]alloc helpers 2017-05-08 17:15:12 -07:00
signalfd.c sched/wait: Rename wait_queue_t => wait_queue_entry_t 2017-06-20 12:18:27 +02:00
splice.c fs: implement vfs_iter_write using do_iter_write 2017-06-29 17:49:23 -04:00
stack.c
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stat.c ufs: restore maintaining ->i_blocks 2017-06-09 16:28:01 -04:00
statfs.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-08 10:50:54 -07:00
super.c VFS: Kill off s_options and helpers 2017-07-11 06:09:21 -04:00
sync.c fs/sync.c: remove unnecessary NULL f_mapping check in sync_file_range 2017-09-06 17:27:28 -07:00
timerfd.c timerfd: Use get_itimerspec64() and put_itimerspec64() 2017-06-30 04:14:38 -04:00
userfaultfd.c mm: userfaultfd: add feature to request for a signal delivery 2017-09-06 17:27:29 -07:00
utimes.c utimes: move compat syscalls from compat.c 2017-04-17 12:52:23 -04:00
xattr.c treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00