Commit Graph

322 Commits

Author SHA1 Message Date
Jens Axboe
88a6f18b95 aio: split out iocb copy from io_submit_one()
In preparation of handing in iocbs in a different fashion as well. Also
make it clear that the iocb being passed in isn't modified, by marking
it const throughout.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-18 08:29:59 -07:00
Jens Axboe
71ebc6fef0 aio: use iocb_put() instead of open coding it
Replace the percpu_ref_put() + kmem_cache_free() with a call to
iocb_put() instead.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-18 08:29:58 -07:00
Jens Axboe
a79d40e9b0 aio: only use blk plugs for > 2 depth submissions
Plugging is meant to optimize submission of a string of IOs, if we don't
have more than 2 being submitted, don't bother setting up a plug.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-18 08:29:58 -07:00
Jens Axboe
2bc4ca9bb6 aio: don't zero entire aio_kiocb aio_get_req()
It's 192 bytes, fairly substantial. Most items don't need to be cleared,
especially not upfront. Clear the ones we do need to clear, and leave
the other ones for setup when the iocb is prepared and submitted.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-18 08:29:58 -07:00
Christoph Hellwig
432c79978c aio: separate out ring reservation from req allocation
This is in preparation for certain types of IO not needing a ring
reserveration.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-18 08:29:58 -07:00
Jens Axboe
bc9bff6162 aio: use assigned completion handler
We know this is a read/write request, but in preparation for
having different kinds of those, ensure that we call the assigned
handler instead of assuming it's aio_complete_rq().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-18 08:29:58 -07:00
Jens Axboe
4b92543282 Merge branch 'for-4.21/block' into for-4.21/aio
* for-4.21/block: (351 commits)
  blk-mq: enable IO poll if .nr_queues of type poll > 0
  blk-mq: change blk_mq_queue_busy() to blk_mq_queue_inflight()
  blk-mq: skip zero-queue maps in blk_mq_map_swqueue
  block: fix blk-iolatency accounting underflow
  blk-mq: fix dispatch from sw queue
  block: mq-deadline: Fix write completion handling
  nvme-pci: don't share queue maps
  blk-mq: only dispatch to non-defauly queue maps if they have queues
  blk-mq: export hctx->type in debugfs instead of sysfs
  blk-mq: fix allocation for queue mapping table
  blk-wbt: export internal state via debugfs
  blk-mq-debugfs: support rq_qos
  block: update sysfs documentation
  block: loop: check error using IS_ERR instead of IS_ERR_OR_NULL in loop_add()
  aoe: add __exit annotation
  block: clear REQ_HIPRI if polling is not supported
  blk-mq: replace and kill blk_mq_request_issue_directly
  blk-mq: issue directly with bypass 'false' in blk_mq_sched_insert_requests
  blk-mq: refactor the code of issue request directly
  block: remove the bio_integrity_advance export
  ...
2018-12-18 08:29:53 -07:00
Linus Torvalds
380ef2c9ad for-linus-20181214
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Merge tag 'for-linus-20181214' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "Three small fixes for this week. contains:

   - spectre indexing fix for aio (Jeff)

   - fix for the previous zeroing bio fix, we don't need it for user
     mapped pages, and in fact it breaks some applications if we do
     (Keith)

   - allocation failure fix for null_blk with zoned (Shin'ichiro)"

* tag 'for-linus-20181214' of git://git.kernel.dk/linux-block:
  block: Fix null_blk_zoned creation failure with small number of zones
  aio: fix spectre gadget in lookup_ioctx
  block/bio: Do not zero user pages
2018-12-14 12:18:30 -08:00
Jeff Moyer
a538e3ff9d aio: fix spectre gadget in lookup_ioctx
Matthew pointed out that the ioctx_table is susceptible to spectre v1,
because the index can be controlled by an attacker.  The below patch
should mitigate the attack for all of the aio system calls.

Cc: stable@vger.kernel.org
Reported-by: Matthew Wilcox <willy@infradead.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-11 11:45:50 -07:00
Christoph Hellwig
154989e45f aio: clear IOCB_HIPRI
No one is going to poll for aio (yet), so we must clear the HIPRI
flag, as we would otherwise send it down the poll queues, where no
one will be polling for completions.

Signed-off-by: Christoph Hellwig <hch@lst.de>

IOCB_HIPRI, not RWF_HIPRI.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-04 09:39:06 -07:00
Jens Axboe
89d04ec349 Linux 4.20-rc5
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Merge tag 'v4.20-rc5' into for-4.21/block

Pull in v4.20-rc5, solving a conflict we'll otherwise get in aio.c and
also getting the merge fix that went into mainline that users are
hitting testing for-4.21/block and/or for-next.

* tag 'v4.20-rc5': (664 commits)
  Linux 4.20-rc5
  PCI: Fix incorrect value returned from pcie_get_speed_cap()
  MAINTAINERS: Update linux-mips mailing list address
  ocfs2: fix potential use after free
  mm/khugepaged: fix the xas_create_range() error path
  mm/khugepaged: collapse_shmem() do not crash on Compound
  mm/khugepaged: collapse_shmem() without freezing new_page
  mm/khugepaged: minor reorderings in collapse_shmem()
  mm/khugepaged: collapse_shmem() remember to clear holes
  mm/khugepaged: fix crashes due to misaccounted holes
  mm/khugepaged: collapse_shmem() stop if punched or truncated
  mm/huge_memory: fix lockdep complaint on 32-bit i_size_read()
  mm/huge_memory: splitting set mapping+index before unfreeze
  mm/huge_memory: rename freeze_page() to unmap_page()
  initramfs: clean old path before creating a hardlink
  kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace
  psi: make disabling/enabling easier for vendor kernels
  proc: fixup map_files test on arm
  debugobjects: avoid recursive calls with kmemleak
  userfaultfd: shmem: UFFDIO_COPY: set the page dirty if VM_WRITE is not set
  ...
2018-12-04 09:38:05 -07:00
Damien Le Moal
76dc891395 aio: Fix fallback I/O priority value
For cases when the application does not specify aio_reqprio for an aio,
fallback to use get_current_ioprio() to obtain the task I/O priority
last set using ioprio_set() rather than the hardcoded IOPRIO_CLASS_NONE
value.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Adam Manzanares <adam.manzanares@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-19 19:03:47 -07:00
Jens Axboe
53fffe29a9 aio: fix failure to put the file pointer
If the ioprio capability check fails, we return without putting
the file pointer.

Fixes: d9a08a9e61 ("fs: Add aio iopriority support")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-11-17 10:05:07 -05:00
Arnd Bergmann
9afc5eee65 y2038: globally rename compat_time to old_time32
Christoph Hellwig suggested a slightly different path for handling
backwards compatibility with the 32-bit time_t based system calls:

Rather than simply reusing the compat_sys_* entry points on 32-bit
architectures unchanged, we get rid of those entry points and the
compat_time types by renaming them to something that makes more sense
on 32-bit architectures (which don't have a compat mode otherwise),
and then share the entry points under the new name with the 64-bit
architectures that use them for implementing the compatibility.

The following types and interfaces are renamed here, and moved
from linux/compat_time.h to linux/time32.h:

old				new
---				---
compat_time_t			old_time32_t
struct compat_timeval		struct old_timeval32
struct compat_timespec		struct old_timespec32
struct compat_itimerspec	struct old_itimerspec32
ns_to_compat_timeval()		ns_to_old_timeval32()
get_compat_itimerspec64()	get_old_itimerspec32()
put_compat_itimerspec64()	put_old_itimerspec32()
compat_get_timespec64()		get_old_timespec32()
compat_put_timespec64()		put_old_timespec32()

As we already have aliases in place, this patch addresses only the
instances that are relevant to the system call interface in particular,
not those that occur in device drivers and other modules. Those
will get handled separately, while providing the 64-bit version
of the respective interfaces.

I'm not renaming the timex, rusage and itimerval structures, as we are
still debating what the new interface will look like, and whether we
will need a replacement at all.

This also doesn't change the names of the syscall entry points, which can
be done more easily when we actually switch over the 32-bit architectures
to use them, at that point we need to change COMPAT_SYSCALL_DEFINEx to
SYSCALL_DEFINEx with a new name, e.g. with a _time32 suffix.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Link: https://lore.kernel.org/lkml/20180705222110.GA5698@infradead.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2018-08-27 14:48:48 +02:00
Linus Torvalds
f2be269897 Merge branch 'work.aio' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs aio updates from Al Viro:
 "Christoph's aio poll, saner this time around.

  This time it's pretty much local to fs/aio.c. Hopefully race-free..."

* 'work.aio' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  aio: allow direct aio poll comletions for keyed wakeups
  aio: implement IOCB_CMD_POLL
  aio: add a iocb refcount
  timerfd: add support for keyed wakeups
2018-08-13 20:56:23 -07:00
Linus Torvalds
a66b4cd1e7 Merge branch 'work.open3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs open-related updates from Al Viro:

 - "do we need fput() or put_filp()" rules are gone - it's always fput()
   now. We keep track of that state where it belongs - in ->f_mode.

 - int *opened mess killed - in finish_open(), in ->atomic_open()
   instances and in fs/namei.c code around do_last()/lookup_open()/atomic_open().

 - alloc_file() wrappers with saner calling conventions are introduced
   (alloc_file_clone() and alloc_file_pseudo()); callers converted, with
   much simplification.

 - while we are at it, saner calling conventions for path_init() and
   link_path_walk(), simplifying things inside fs/namei.c (both on
   open-related paths and elsewhere).

* 'work.open3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits)
  few more cleanups of link_path_walk() callers
  allow link_path_walk() to take ERR_PTR()
  make path_init() unconditionally paired with terminate_walk()
  document alloc_file() changes
  make alloc_file() static
  do_shmat(): grab shp->shm_file earlier, switch to alloc_file_clone()
  new helper: alloc_file_clone()
  create_pipe_files(): switch the first allocation to alloc_file_pseudo()
  anon_inode_getfile(): switch to alloc_file_pseudo()
  hugetlb_file_setup(): switch to alloc_file_pseudo()
  ocxlflash_getfile(): switch to alloc_file_pseudo()
  cxl_getfile(): switch to alloc_file_pseudo()
  ... and switch shmem_file_setup() to alloc_file_pseudo()
  __shmem_file_setup(): reorder allocations
  new wrapper: alloc_file_pseudo()
  kill FILE_{CREATED,OPENED}
  switch atomic_open() and lookup_open() to returning 0 in all success cases
  document ->atomic_open() changes
  ->atomic_open(): return 0 in all success cases
  get rid of 'opened' in path_openat() and the helpers downstream
  ...
2018-08-13 19:58:36 -07:00
Christoph Hellwig
e8693bcfa0 aio: allow direct aio poll comletions for keyed wakeups
If we get a keyed wakeup for a aio poll waitqueue and wake can acquire the
ctx_lock without spinning we can just complete the iocb straight from the
wakeup callback to avoid a context switch.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Avi Kivity <avi@scylladb.com>
2018-08-06 10:24:39 +02:00
Christoph Hellwig
bfe4037e72 aio: implement IOCB_CMD_POLL
Simple one-shot poll through the io_submit() interface.  To poll for
a file descriptor the application should submit an iocb of type
IOCB_CMD_POLL.  It will poll the fd for the events specified in the
the first 32 bits of the aio_buf field of the iocb.

Unlike poll or epoll without EPOLLONESHOT this interface always works
in one shot mode, that is once the iocb is completed, it will have to be
resubmitted.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Avi Kivity <avi@scylladb.com>
2018-08-06 10:24:33 +02:00
Christoph Hellwig
9018ccc453 aio: add a iocb refcount
This is needed to prevent races caused by the way the ->poll API works.
To avoid introducing overhead for other users of the iocbs we initialize
it to zero and only do refcount operations if it is non-zero in the
completion path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Avi Kivity <avi@scylladb.com>
2018-08-06 10:24:28 +02:00
Linus Torvalds
165ea0d1c2 Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs fixes from Al Viro:
 "Fix several places that screw up cleanups after failures halfway
  through opening a file (one open-coding filp_clone_open() and getting
  it wrong, two misusing alloc_file()). That part is -stable fodder from
  the 'work.open' branch.

  And Christoph's regression fix for uapi breakage in aio series;
  include/uapi/linux/aio_abi.h shouldn't be pulling in the kernel
  definition of sigset_t, the reason for doing so in the first place had
  been bogus - there's no need to expose struct __aio_sigset in
  aio_abi.h at all"

* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  aio: don't expose __aio_sigset in uapi
  ocxlflash_getfile(): fix double-iput() on alloc_file() failures
  cxl_getfile(): fix double-iput() on alloc_file() failures
  drm_mode_create_lease_ioctl(): fix open-coded filp_clone_open()
2018-07-22 12:04:51 -07:00
Christoph Hellwig
9ba546c019 aio: don't expose __aio_sigset in uapi
glibc uses a different defintion of sigset_t than the kernel does,
and the current version would pull in both.  To fix this just do not
expose the type at all - this somewhat mirrors pselect() where we
do not even have a type for the magic sigmask argument, but just
use pointer arithmetics.

Fixes: 7a074e96 ("aio: implement io_pgetevents")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Adrian Reber <adrian@lisas.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-17 23:26:58 -04:00
Al Viro
d93aa9d82a new wrapper: alloc_file_pseudo()
takes inode, vfsmount, name, O_... flags and file_operations and
either returns a new struct file (in which case inode reference we
held is consumed) or returns ERR_PTR(), in which case no refcounts
are altered.

converted aio_private_file() and sock_alloc_file() to it

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12 10:04:23 -04:00
Al Viro
c9c554f214 alloc_file(): switch to passing O_... flags instead of FMODE_... mode
... so that it could set both ->f_flags and ->f_mode, without callers
having to set ->f_flags manually.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12 10:02:57 -04:00
Linus Torvalds
a11e1d432b Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL
The poll() changes were not well thought out, and completely
unexplained.  They also caused a huge performance regression, because
"->poll()" was no longer a trivial file operation that just called down
to the underlying file operations, but instead did at least two indirect
calls.

Indirect calls are sadly slow now with the Spectre mitigation, but the
performance problem could at least be largely mitigated by changing the
"->get_poll_head()" operation to just have a per-file-descriptor pointer
to the poll head instead.  That gets rid of one of the new indirections.

But that doesn't fix the new complexity that is completely unwarranted
for the regular case.  The (undocumented) reason for the poll() changes
was some alleged AIO poll race fixing, but we don't make the common case
slower and more complex for some uncommon special case, so this all
really needs way more explanations and most likely a fundamental
redesign.

[ This revert is a revert of about 30 different commits, not reverted
  individually because that would just be unnecessarily messy  - Linus ]

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-06-28 10:40:47 -07:00
Christoph Hellwig
2739b807b0 aio: only return events requested in poll_mask() for IOCB_CMD_POLL
The ->poll_mask() operation has a mask of events that the caller
is interested in, but not all implementations might take it into
account.  Mask the return value to only the requested events,
similar to what the poll and epoll code does.

Reported-by: Avi Kivity <avi@scylladb.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-06-14 20:08:14 -04:00
Adam Manzanares
9a6d9a62e0 fs: aio ioprio use ioprio_check_cap ret val
Previously the value was ignored.

Signed-off-by: Adam Manzanares <adam.manzanares@wdc.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-06-04 14:20:39 -04:00
Adam Manzanares
d9a08a9e61 fs: Add aio iopriority support
This is the per-I/O equivalent of the ioprio_set system call.

When IOCB_FLAG_IOPRIO is set on the iocb aio_flags field, then we set the
newly added kiocb ki_ioprio field to the value in the iocb aio_reqprio field.

This patch depends on block: add ioprio_check_cap function.

Signed-off-by: Adam Manzanares <adam.manzanares@wdc.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-31 10:50:55 -04:00
Adam Manzanares
fc28724d67 fs: Convert kiocb rw_hint from enum to u16
In order to avoid kiocb bloat for per command iopriority support, rw_hint
is converted from enum to a u16. Added a guard around ki_hint assignment.

Signed-off-by: Adam Manzanares <adam.manzanares@wdc.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-31 10:50:54 -04:00
Al Viro
1da92779e2 aio: sanitize the limit checking in io_submit(2)
as it is, the logics in native io_submit(2) is "if asked for
more than LONG_MAX/sizeof(pointer) iocbs to submit, don't
bother with more than LONG_MAX/sizeof(pointer)" (i.e.
512M requests on 32bit and 1E requests on 64bit) while
compat io_submit(2) goes with "stop after the first
PAGE_SIZE/sizeof(pointer) iocbs", i.e. 1K or so.  Which is
	* inconsistent
	* *way* too much in native case
	* possibly too little in compat one
and
	* wrong anyway, since the natural point where we
ought to stop bothering is ctx->nr_events

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-29 23:20:17 -04:00
Al Viro
67ba049f94 aio: fold do_io_submit() into callers
get rid of insane "copy array of 32bit pointers into an array of
native ones" glue.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-29 23:19:29 -04:00
Al Viro
95af8496ac aio: shift copyin of iocb into io_submit_one()
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-29 23:18:31 -04:00
Al Viro
d2988bd412 aio_read_events_ring(): make a bit more readable
The logics for 'avail' is
	* not past the tail of cyclic buffer
	* no more than asked
	* not past the end of buffer
	* not past the end of a page

Unobfuscate the last part.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-29 23:18:17 -04:00
Al Viro
9061d14a8a aio: all callers of aio_{read,write,fsync,poll} treat 0 and -EIOCBQUEUED the same way
... so just make them return 0 when caller does not need to destroy iocb

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-29 23:17:40 -04:00
Al Viro
3c96c7f4ca aio: take list removal to (some) callers of aio_complete()
We really want iocb out of io_cancel(2) reach before we start tearing
it down.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-29 23:16:43 -04:00
Christoph Hellwig
ac060cbaa8 aio: add missing break for the IOCB_CMD_FDSYNC case
Looks like this got lost in a merge.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-28 13:40:50 -04:00
Christoph Hellwig
1962da0d21 aio: try to complete poll iocbs without context switch
If we can acquire ctx_lock without spinning we can just remove our
iocb from the active_reqs list, and thus complete the iocbs from the
wakeup context.

Signed-off-by: Christoph Hellwig <hch@lst.de>
2018-05-26 09:16:44 +02:00
Christoph Hellwig
2c14fa838c aio: implement IOCB_CMD_POLL
Simple one-shot poll through the io_submit() interface.  To poll for
a file descriptor the application should submit an iocb of type
IOCB_CMD_POLL.  It will poll the fd for the events specified in the
the first 32 bits of the aio_buf field of the iocb.

Unlike poll or epoll without EPOLLONESHOT this interface always works
in one shot mode, that is once the iocb is completed, it will have to be
resubmitted.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-05-26 09:16:44 +02:00
Christoph Hellwig
888933f8fd aio: simplify cancellation
With the current aio code there is no need for the magic KIOCB_CANCELLED
value, as a cancelation just kicks the driver to queue the completion
ASAP, with all actual completion handling done in another thread. Given
that both the completion path and cancelation take the context lock there
is no need for magic cmpxchg loops either.  If we remove iocbs from the
active list after calling ->ki_cancel (but with ctx_lock still held), we
can also rely on the invariant thay anything found on the list has a
->ki_cancel callback and can be cancelled, further simplifing the code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
2018-05-26 09:16:44 +02:00
Christoph Hellwig
f3a2752a43 aio: simplify KIOCB_KEY handling
No need to pass the key field to lookup_iocb to compare it with KIOCB_KEY,
as we can do that right after retrieving it from userspace.  Also move the
KIOCB_KEY definition to aio.c as it is an internal value not used by any
other place in the kernel.

Signed-off-by: Christoph Hellwig <hch@lst.de>
2018-05-26 09:16:44 +02:00
Christoph Hellwig
ed0d523adb Merge branch 'fixes' of https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs into aio-base 2018-05-26 09:16:25 +02:00
Al Viro
4faa99965e fix io_destroy()/aio_complete() race
If io_destroy() gets to cancelling everything that can be cancelled and
gets to kiocb_cancel() calling the function driver has left in ->ki_cancel,
it becomes vulnerable to a race with IO completion.  At that point req
is already taken off the list and aio_complete() does *NOT* spin until
we (in free_ioctx_users()) releases ->ctx_lock.  As the result, it proceeds
to kiocb_free(), freing req just it gets passed to ->ki_cancel().

Fix is simple - remove from the list after the call of kiocb_cancel().  All
instances of ->ki_cancel() already have to cope with the being called with
iocb still on list - that's what happens in io_cancel(2).

Cc: stable@kernel.org
Fixes: 0460fef2a9 "aio: use cancellation list lazily"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-23 22:53:22 -04:00
Al Viro
baf10564fb aio: fix io_destroy(2) vs. lookup_ioctx() race
kill_ioctx() used to have an explicit RCU delay between removing the
reference from ->ioctx_table and percpu_ref_kill() dropping the refcount.
At some point that delay had been removed, on the theory that
percpu_ref_kill() itself contained an RCU delay.  Unfortunately, that was
the wrong kind of RCU delay and it didn't care about rcu_read_lock() used
by lookup_ioctx().  As the result, we could get ctx freed right under
lookup_ioctx().  Tejun has fixed that in a6d7cff472 ("fs/aio: Add explicit
RCU grace period when freeing kioctx"); however, that fix is not enough.

Suppose io_destroy() from one thread races with e.g. io_setup() from another;
CPU1 removes the reference from current->mm->ioctx_table[...] just as CPU2
has picked it (under rcu_read_lock()).  Then CPU1 proceeds to drop the
refcount, getting it to 0 and triggering a call of free_ioctx_users(),
which proceeds to drop the secondary refcount and once that reaches zero
calls free_ioctx_reqs().  That does
        INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
        queue_rcu_work(system_wq, &ctx->free_rwork);
and schedules freeing the whole thing after RCU delay.

In the meanwhile CPU2 has gotten around to percpu_ref_get(), bumping the
refcount from 0 to 1 and returned the reference to io_setup().

Tejun's fix (that queue_rcu_work() in there) guarantees that ctx won't get
freed until after percpu_ref_get().  Sure, we'd increment the counter before
ctx can be freed.  Now we are out of rcu_read_lock() and there's nothing to
stop freeing of the whole thing.  Unfortunately, CPU2 assumes that since it
has grabbed the reference, ctx is *NOT* going away until it gets around to
dropping that reference.

The fix is obvious - use percpu_ref_tryget_live() and treat failure as miss.
It's not costlier than what we currently do in normal case, it's safe to
call since freeing *is* delayed and it closes the race window - either
lookup_ioctx() comes before percpu_ref_kill() (in which case ctx->users
won't reach 0 until the caller of lookup_ioctx() drops it) or lookup_ioctx()
fails, ctx->users is unaffected and caller of lookup_ioctx() doesn't see
the object in question at all.

Cc: stable@kernel.org
Fixes: a6d7cff472 "fs/aio: Add explicit RCU grace period when freeing kioctx"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-21 14:30:11 -04:00
Christoph Hellwig
7a074e96de aio: implement io_pgetevents
This is the io_getevents equivalent of ppoll/pselect and allows to
properly mix signals and aio completions (especially with IOCB_CMD_POLL)
and atomically executes the following sequence:

	sigset_t origmask;

	pthread_sigmask(SIG_SETMASK, &sigmask, &origmask);
	ret = io_getevents(ctx, min_nr, nr, events, timeout);
	pthread_sigmask(SIG_SETMASK, &origmask, NULL);

Note that unlike many other signal related calls we do not pass a sigmask
size, as that would get us to 7 arguments, which aren't easily supported
by the syscall infrastructure.  It seems a lot less painful to just add a
new syscall variant in the unlikely case we're going to increase the
sigset size.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-05-02 19:57:24 +02:00
Christoph Hellwig
a3c0d439e4 aio: implement IOCB_CMD_FSYNC and IOCB_CMD_FDSYNC
Simple workqueue offload for now, but prepared for adding a real aio_fsync
method if the need arises.  Based on an earlier patch from Dave Chinner.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-05-02 19:57:24 +02:00
Christoph Hellwig
54843f875f aio: refactor read/write iocb setup
Don't reference the kiocb structure from the common aio code, and move
any use of it into helper specific to the read/write path.  This is in
preparation for aio_poll support that wants to use the space for different
fields.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-05-02 19:57:21 +02:00
Christoph Hellwig
92ce472856 aio: remove the extra get_file/fput pair in io_submit_one
If we release the lockdep write protection token before calling into
->write_iter and thus never access the file pointer after an -EIOCBQUEUED
return from ->write_iter or ->read_iter we don't need this extra
reference.

Signed-off-by: Christoph Hellwig <hch@lst.de>
2018-05-02 19:56:30 +02:00
Christoph Hellwig
75321b50a3 aio: sanitize ki_list handling
Instead of handcoded non-null checks always initialize ki_list to an
empty list and use list_empty / list_empty_careful on it.  While we're
at it also error out on a double call to kiocb_set_cancel_fn instead
of ignoring it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-05-02 19:52:59 +02:00
Christoph Hellwig
c213dc826c aio: remove an outdated BUG_ON and comment in aio_complete
These days we don't treat sync iocbs special in the aio completion code as
they never use it.  Remove the old comment and BUG_ON given that the
current definition of is_sync_kiocb makes it impossible to hit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-05-02 19:52:38 +02:00
Christoph Hellwig
01a658e1e9 aio: don't print the page size at boot time
The page size is in no way related to the aio code, and printing it in
the (debug) dmesg at every boot serves no purpose.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-05-02 19:48:36 +02:00
Tejun Heo
f729863a8c fs/aio: Use rcu_work instead of explicit rcu and work item
Workqueue now has rcu_work.  Use it instead of open-coding rcu -> work
item bouncing.

Signed-off-by: Tejun Heo <tj@kernel.org>
2018-03-19 10:12:03 -07:00