Commit Graph

20 Commits

Author SHA1 Message Date
Vegard Nossum
ffecee4f24 iov_iter: kernel-doc import_iovec() and rw_copy_check_uvector()
Both import_iovec() and rw_copy_check_uvector() take an array
(typically small and on-stack) which is used to hold an iovec array copy
from userspace. This is to avoid an expensive memory allocation in the
fast path (i.e. few iovec elements).

The caller may have to check whether these functions actually used
the provided buffer or allocated a new one -- but this differs between
the too. Let's just add a kernel doc to clarify what the semantics are
for each function.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-14 20:00:34 -04:00
Al Viro
1689c73a73 Fix off-by-one in __pipe_get_pages()
it actually worked only when requested area ended on the page boundary...

Reported-by: Marco Grassi <marco.gra@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 10:40:01 -07:00
Linus Torvalds
abb5a14fa2 Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull misc vfs updates from Al Viro:
 "Assorted misc bits and pieces.

  There are several single-topic branches left after this (rename2
  series from Miklos, current_time series from Deepa Dinamani, xattr
  series from Andreas, uaccess stuff from from me) and I'd prefer to
  send those separately"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (39 commits)
  proc: switch auxv to use of __mem_open()
  hpfs: support FIEMAP
  cifs: get rid of unused arguments of CIFSSMBWrite()
  posix_acl: uapi header split
  posix_acl: xattr representation cleanups
  fs/aio.c: eliminate redundant loads in put_aio_ring_file
  fs/internal.h: add const to ns_dentry_operations declaration
  compat: remove compat_printk()
  fs/buffer.c: make __getblk_slow() static
  proc: unsigned file descriptors
  fs/file: more unsigned file descriptors
  fs: compat: remove redundant check of nr_segs
  cachefiles: Fix attempt to read i_blocks after deleting file [ver #2]
  cifs: don't use memcpy() to copy struct iov_iter
  get rid of separate multipage fault-in primitives
  fs: Avoid premature clearing of capabilities
  fs: Give dentry to inode_change_ok() instead of inode
  fuse: Propagate dentry down to inode_change_ok()
  ceph: Propagate dentry down to inode_change_ok()
  xfs: Propagate dentry down to inode_change_ok()
  ...
2016-10-10 13:04:49 -07:00
Miklos Szeredi
a779638cf6 pipe: add pipe_buf_release() helper
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-05 18:23:58 -04:00
Al Viro
241699cd72 new iov_iter flavour: pipe-backed
iov_iter variant for passing data into pipe.  copy_to_iter()
copies data into page(s) it has allocated and stuffs them into
the pipe; copy_page_to_iter() stuffs there a reference to the
page given to it.  Both will try to coalesce if possible.
iov_iter_zero() is similar to copy_to_iter(); iov_iter_get_pages()
and friends will do as copy_to_iter() would have and return the
pages where the data would've been copied.  iov_iter_advance()
will truncate everything past the spot it has advanced to.

New primitive: iov_iter_pipe(), used for initializing those.
pipe should be locked all along.

Running out of space acts as fault would for iovec-backed ones;
in other words, giving it to ->read_iter() may result in short
read if the pipe overflows, or -EFAULT if it happens with nothing
copied there.

In other words, ->read_iter() on those acts pretty much like
->splice_read().  Moreover, all generic_file_splice_read() users,
as well as many other ->splice_read() instances can be switched
to that scheme - that'll happen in the next commit.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-05 18:23:36 -04:00
Al Viro
4bce9f6ee8 get rid of separate multipage fault-in primitives
* the only remaining callers of "short" fault-ins are just as happy with generic
variants (both in lib/iov_iter.c); switch them to multipage variants, kill the
"short" ones
* rename the multipage variants to now available plain ones.
* get rid of compat macro defining iov_iter_fault_in_multipage_readable by
expanding it in its only user.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-09-27 18:12:24 -04:00
Al Viro
d4690f1e1c fix iov_iter_fault_in_readable()
... by turning it into what used to be multipages counterpart

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-09-17 14:05:30 -07:00
Mikulas Patocka
3fa6c50731 mm: optimize copy_page_to/from_iter_iovec
copy_page_to_iter_iovec() and copy_page_from_iter_iovec() copy some data
to userspace or from userspace.  These functions have a fast path where
they map a page using kmap_atomic and a slow path where they use kmap.

kmap is slower than kmap_atomic, so the fast path is preferred.

However, on kernels without highmem support, kmap just calls
page_address, so there is no need to avoid kmap.  On kernels without
highmem support, the fast path just increases code size (and cache
footprint) and it doesn't improve copy performance in any way.

This patch enables the fast path only if CONFIG_HIGHMEM is defined.

Code size reduced by this patch:
  x86 (without highmem)	  928
  x86-64		  960
  sparc64		  848
  alpha			 1136
  pa-risc		 1200

[akpm@linux-foundation.org: use IS_ENABLED(), per Andi]
Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1607221711410.4818@file01.intranet.prod.int.rdu2.redhat.com
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-28 16:07:41 -07:00
Ming Lei
1bdc76aea1 iov_iter: use bvec iterator to implement iterate_bvec()
bvec has one native/mature iterator for long time, so not
necessary to use the reinvented wheel for iterating bvecs
in lib/iov_iter.c.

Two ITER_BVEC test cases are run:
	- xfstest(-g auto) on loop dio/aio, no regression found
	- swap file works well under extreme stress(stress-ng --all 64 -t
	  800 -v), and lots of OOMs are triggerd, and the whole
	system still survives

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Tested-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-06-09 10:02:47 -06:00
Linus Torvalds
0985b65d3b Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs iov_iter regression fix from Al Viro:
 "Fix for braino in 'fold checks into iterate_and_advance()'"

* 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  do "fold checks into iterate_and_advance()" right
2016-05-25 15:59:09 -07:00
Al Viro
19f1845933 do "fold checks into iterate_and_advance()" right
the only case when we should skip the iterate_and_advance() guts
is when nothing's left in the iterator, _not_ just when requested
amount is 0.  Said guts will do nothing in the latter case anyway;
the problem we tried to deal with in the aforementioned commit is
that when there's nothing left *and* the amount requested is 0,
we might end up deferencing one iovec too many; the value we fetch
from there is discarded in that case, but theoretically it might
oops if the iovec array ends exactly at the end of page with the
next page not mapped.

Bailing out on zero size requested had an unexpected side effect -
zero-length segment in the beginning of iovec array ended up
throwing do_loop_readv_writev() into infinite spin; we do not
advance past the empty segment at all.  Reproducer is trivial:
echo '#include <sys/uio.h>' >a.c
echo 'main() {char c; struct iovec v[] = {{&c,0},{&c,1}}; readv(0,v,2);}' >>a.c
cc a.c && ./a.out </proc/uptime

which should end up with the process not hanging.  Probably ought to
go into LTP or xfstests...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-05-25 18:16:02 -04:00
Linus Torvalds
69370471d0 Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull iov_iter cleanups from Al Viro.

* 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fold checks into iterate_and_advance()
  rw_verify_area(): saner calling conventions
  aio: remove a pointless assignment
2016-05-18 11:46:23 -07:00
Al Viro
dd254f5a38 fold checks into iterate_and_advance()
they are open-coded in all users except iov_iter_advance(), and there
they wouldn't be a bad idea either - as it is, iov_iter_advance(i, 0)
ends up dereferencing potentially past the end of iovec array.  It
doesn't do anything with the value it reads, and very unlikely to
trigger an oops on dereference, but it is not impossible.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-05-09 14:04:29 -04:00
Al Viro
357f435d8a fix the copy vs. map logics in blk_rq_map_user_iov()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-04-08 19:46:28 -04:00
Al Viro
e12675853d iov_iter: export import_single_range()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-12-06 20:42:19 -05:00
Al Viro
36f7a8a4cd iov_iter: constify {csum_and_,}copy_to_iter()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-12-06 20:42:15 -05:00
Al Viro
36e9f6535f Merge branch 'iov_iter' into for-next 2015-04-11 22:26:51 -04:00
Anton Altaparmakov
171a02032b VFS: Add iov_iter_fault_in_multipages_readable()
simillar to iov_iter_fault_in_readable() but differs in that it is
not limited to faulting in the first iovec and instead faults in
"bytes" bytes iterating over the iovecs as necessary.

Also, instead of only faulting in the first and last page of the
range, all pages are faulted in.

This function is needed by NTFS when it does multi page file
writes.

Signed-off-by: Anton Altaparmakov <anton@tuxera.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-04-11 22:24:32 -04:00
Al Viro
bc917be810 saner iov_iter initialization primitives
iovec-backed iov_iter instances are assumed to satisfy several properties:
	* no more than UIO_MAXIOV elements in iovec array
	* total size of all ranges is no more than MAX_RW_COUNT
	* all ranges pass access_ok().

The problem is, invariants of data structures should be established in the
primitives creating those data structures, not in the code using those
primitives.  And iov_iter_init() violates that principle.  For a while we
managed to get away with that, but once the use of iov_iter started to
spread, it didn't take long for shit to hit the fan - missed check in
sys_sendto() had introduced a roothole.

We _do_ have primitives for importing and validating iovecs (both native and
compat ones) and those primitives are almost always followed by shoving the
resulting iovec into iov_iter.  Life would be considerably simpler (and safer)
if we combined those primitives with initializing iov_iter.

That gives us two new primitives - import_iovec() and compat_import_iovec().
Calling conventions:
	iovec = iov_array;
	err = import_iovec(direction, uvec, nr_segs,
			   ARRAY_SIZE(iov_array), &iovec,
			   &iter);
imports user vector into kernel space (into iov_array if it fits, allocated
if it doesn't fit or if iovec was NULL), validates it and sets iter up to
refer to it.  On success 0 is returned and allocated kernel copy (or NULL
if the array had fit into caller-supplied one) is returned via iovec.
On failure all allocations are undone and -E... is returned.  If the total
size of ranges exceeds MAX_RW_COUNT, the excess is silently truncated.

compat_import_iovec() expects uvec to be a pointer to user array of compat_iovec;
otherwise it's identical to import_iovec().

Finally, import_single_range() sets iov_iter backed by single-element iovec
covering a user-supplied range -

	err = import_single_range(direction, address, size, iovec, &iter);

does validation and sets iter up.  Again, size in excess of MAX_RW_COUNT gets
silently truncated.

Next commits will be switching the things up to use of those and reducing
the amount of iov_iter_init() instances.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-03-30 11:08:16 -04:00
Al Viro
d879cb8341 move iov_iter.c from mm/ to lib/
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-02-17 22:22:17 -05:00