linux.git/fs/splice.c, branch v6.3

splice: Remove redundant assignment to ret

2023-03-09T09:10:31+00:00

The variable ret belongs to redundant assignment and can be deleted.

fs/splice.c:940:2: warning: Value stored to 'ret' is never read.

Reported-by: Abaci Robot 
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=4406
Signed-off-by: Jiapeng Chong 
Reviewed-by: Chaitanya Kulkarni 
Signed-off-by: Christian Brauner (Microsoft)

Merge tag '6.3-rc-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6

2023-02-23T01:12:44+00:00

Pull cifs client updates from Steve French:
 "The largest subset of this is from David Howells et al: making the
  cifs/smb3 driver pass iov_iters down to the lowest layers, directly to
  the network transport rather than passing lists of pages around,
  helping multiple areas:

   - Pin user pages, thereby fixing the race between concurrent DIO read
     and fork, where the pages containing the DIO read buffer may end up
     belonging to the child process and not the parent - with the result
     that the parent might not see the retrieved data.

   - cifs shouldn't take refs on pages extracted from non-user-backed
     iterators (eg. KVEC). With these changes, cifs will apply the
     appropriate cleanup.

   - Making it easier to transition to using folios in cifs rather than
     pages by dealing with them through BVEC and XARRAY iterators.

   - Allowing cifs to use the new splice function

  The remainder are:

   - fixes for stable, including various fixes for uninitialized memory,
     wrong length field causing mount issue to very old servers,
     important directory lease fixes and reconnect fixes

   - cleanups (unused code removal, change one element array usage, and
     a change form strtobool to kstrtobool, and Kconfig cleanups)

   - SMBDIRECT (RDMA) fixes including iov_iter integration and UAF fixes

   - reconnect fixes

   - multichannel fixes, including improving channel allocation (to
     least used channel)

   - remove the last use of lock_page_killable by moving to
     folio_lock_killable"

* tag '6.3-rc-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6: (46 commits)
  update internal module version number for cifs.ko
  cifs: update ip_addr for ses only for primary chan setup
  cifs: use tcon allocation functions even for dummy tcon
  cifs: use the least loaded channel for sending requests
  cifs: DIO to/from KVEC-type iterators should now work
  cifs: Remove unused code
  cifs: Build the RDMA SGE list directly from an iterator
  cifs: Change the I/O paths to use an iterator rather than a page list
  cifs: Add a function to read into an iter from a socket
  cifs: Add some helper functions
  cifs: Add a function to Hash the contents of an iterator
  cifs: Add a function to build an RDMA SGE list from an iterator
  netfs: Add a function to extract an iterator into a scatterlist
  netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator
  cifs: Implement splice_read to pass down ITER_BVEC not ITER_PIPE
  splice: Export filemap/direct_splice_read()
  iov_iter: Add a function to extract a page list from an iterator
  iov_iter: Define flags to qualify page extraction.
  splice: Add a func to do a splice from an O_DIRECT file without ITER_PIPE
  splice: Add a func to do a splice from a buffered file without ITER_PIPE
  ...

splice: Export filemap/direct_splice_read()

2023-02-20T23:25:43+00:00

filemap_splice_read() and direct_splice_read() should be exported.

Signed-off-by: David Howells 
cc: Steve French 
cc: Jens Axboe 
cc: Christoph Hellwig 
cc: Al Viro 
cc: David Hildenbrand 
cc: John Hubbard 
cc: linux-cifs@vger.kernel.org
cc: linux-mm@kvack.org
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French

splice: Add a func to do a splice from an O_DIRECT file without ITER_PIPE

2023-02-20T23:25:43+00:00

Implement a function, direct_file_splice(), that deals with this by using
an ITER_BVEC iterator instead of an ITER_PIPE iterator as the former won't
free its buffers when reverted.  The function bulk allocates all the
buffers it thinks it is going to use in advance, does the read
synchronously and only then trims the buffer down.  The pages we did use
get pushed into the pipe.

This fixes a problem with the upcoming iov_iter_extract_pages() function,
whereby pages extracted from a non-user-backed iterator such as ITER_PIPE
aren't pinned.  __iomap_dio_rw(), however, calls iov_iter_revert() to
shorten the iterator to just the bufferage it is going to use - which has
the side-effect of freeing the excess pipe buffers, even though they're
attached to a bio and may get written to by DMA (thanks to Hillf Danton for
spotting this[1]).

This then causes memory corruption that is particularly noticeable when the
syzbot test[2] is run.  The test boils down to:

	out = creat(argv[1], 0666);
	ftruncate(out, 0x800);
	lseek(out, 0x200, SEEK_SET);
	in = open(argv[1], O_RDONLY | O_DIRECT | O_NOFOLLOW);
	sendfile(out, in, NULL, 0x1dd00);

run repeatedly in parallel.  What I think is happening is that ftruncate()
occasionally shortens the DIO read that's about to be made by sendfile's
splice core by reducing i_size.

This should be more efficient for DIO read by virtue of doing a bulk page
allocation, but slightly less efficient by ignoring any partial page in the
pipe.

Reported-by: syzbot+a440341a59e3b7142895@syzkaller.appspotmail.com
Signed-off-by: David Howells 
Reviewed-by: Jens Axboe 
cc: Christoph Hellwig 
cc: Al Viro 
cc: David Hildenbrand 
cc: John Hubbard 
cc: linux-mm@kvack.org
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20230207094731.1390-1-hdanton@sina.com/ [1]
Link: https://lore.kernel.org/r/000000000000b0b3c005f3a09383@google.com/ [2]
Signed-off-by: Steve French

splice: use bvec_set_page to initialize a bvec

2023-02-03T17:17:42+00:00

Use the bvec_set_page helper to initialize a bvec.

Signed-off-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/20230203150634.3199647-18-hch@lst.de
Signed-off-by: Jens Axboe

use less confusing names for iov_iter direction initializers

2022-11-25T18:01:55+00:00

READ/WRITE proved to be actively confusing - the meanings are
"data destination, as used with read(2)" and "data source, as
used with write(2)", but people keep interpreting those as
"we read data from it" and "we write data to it", i.e. exactly
the wrong way.

Call them ITER_DEST and ITER_SOURCE - at least that is harder
to misinterpret...

Signed-off-by: Al Viro

iter_to_pipe(): switch to advancing variant of iov_iter_get_pages()

2022-08-09T02:37:23+00:00

... and untangle the cleanup on failure to add into pipe.

Reviewed-by: Jeff Layton 
Signed-off-by: Al Viro

splice: stop abusing iov_iter_advance() to flush a pipe

2022-08-09T02:37:16+00:00

Use pipe_discard_from() explicitly in generic_file_read_iter(); don't bother
with rather non-obvious use of iov_iter_advance() in there.

Reviewed-by: Jeff Layton 
Reviewed-by: Christian Brauner (Microsoft) 
Signed-off-by: Al Viro

fs: check FMODE_LSEEK to control internal pipe splicing

2022-07-16T13:19:16+00:00

The original direct splicing mechanism from Jens required the input to
be a regular file because it was avoiding the special socket case. It
also recognized blkdevs as being close enough to a regular file. But it
forgot about chardevs, which behave the same way and work fine here.

This is an okayish heuristic, but it doesn't totally work. For example,
a few chardevs should be spliceable here. And a few regular files
shouldn't. This patch fixes this by instead checking whether FMODE_LSEEK
is set, which represents decently enough what we need rewinding for when
splicing to internal pipes.

Fixes: b92ce5589374 ("[PATCH] splice: add direct fd <-> fd splicing support")
Cc: Jens Axboe 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Al Viro

mm: Convert remove_mapping() to take a folio

2022-03-21T16:59:01+00:00

Add kernel-doc and return the number of pages removed in order to
get the statistics right in __invalidate_mapping_pages().

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Miaohe Lin