Commit Graph

63 Commits

Author SHA1 Message Date
Dave Jones
9aefe431f5 [PATCH] splice: potential !page dereference
We can get to out: with a NULL page, which we probably
don't want to be calling page_cache_release() on.

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-10 09:02:40 +02:00
Jens Axboe
c7f21e4f5a [PATCH] splice: mark the io page as accessed
We should do that, since we do the LRU manipulation ourselves now. Suggested
by Nick Piggin.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-10 09:01:01 +02:00
Jens Axboe
3e7ee3e7b3 [PATCH] splice: fix page stealing LRU handling.
Originally from Nick Piggin, just adapted to the newer branch.

You can't check PageLRU without holding zone->lru_lock.  The page
release code can get away with it only because the page refcount is 0 at
that point. Also, you can't reliably remove pages from the LRU unless
the refcount is 0. Ever.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-02 23:11:04 +02:00
Jens Axboe
ad8d6f0a78 [PATCH] splice: page stealing needs to wait_on_page_writeback()
Thanks to Andrew for the good explanation of why this is so. akpm writes:

If a page is under writeback and we remove it from pagecache, it's still
going to get written to disk.  But the VFS no longer knows about that page,
nor that this page is about to modify disk blocks.

So there might be scenarios in which those
blocks-which-are-about-to-be-written-to get reused for something else.
When writeback completes, it'll scribble on those blocks.

This won't happen in ext2/ext3-style filesystems in normal mode because the
page has buffers and try_to_release_page() will fail.

But ext2 in nobh mode doesn't attach buffers at all - it just sticks the
page in a BIO, finds some new blocks, points the BIO at those blocks and
lets it rip.

While that write IO's in flight, someone could truncate the file.  Truncate
won't block on the writeout because the page isn't in pagecache any more.
So truncate will the free the blocks from the file under the page's feet.
Then something else can reallocate those blocks.  Then write data to them.

Now, the original write completes, corrupting the filesystem.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-02 23:10:32 +02:00
Jens Axboe
059a8f3734 [PATCH] splice: export generic_splice_sendpage
Forgot that one, thanks Jeff. Also move the other EXPORT_SYMBOL
to right below the functions.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-02 23:06:05 +02:00
Jens Axboe
b2b39fa478 [PATCH] splice: add a SPLICE_F_MORE flag
This lets userspace indicate whether more data will be coming in a
subsequent splice call.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-02 23:05:41 +02:00
Jens Axboe
83f9135bdd [PATCH] splice: add comments documenting more of the code
Hopefully this will make Andrew a little more happy.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-02 23:05:09 +02:00
Jens Axboe
4f6f0bd2ff [PATCH] splice: improve writeback and clean up page stealing
By cleaning up the writeback logic (killing write_one_page() and the manual
set_page_dirty()), we can get rid of ->stolen inside the pipe_buffer and
just keep it local in pipe_to_file().

This also adds dirty page balancing logic and O_SYNC handling.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-02 23:04:46 +02:00
Jens Axboe
53cd9ae886 [PATCH] splice: fix shadow[] filling logic
Clear the entire range, and don't increment pidx or we keep filling
the same position again and again.

Thanks to KAMEZAWA Hiroyuki.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-04-02 23:04:21 +02:00
Linus Torvalds
29e350944f splice: add SPLICE_F_NONBLOCK flag
It doesn't make the splice itself necessarily nonblocking (because the
actual file descriptors that are spliced from/to may block unless they
have the O_NONBLOCK flag set), but it makes the splice pipe operations
nonblocking.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-04-02 12:46:35 -07:00
Jeff Garzik
a0f0678025 [PATCH] splice exports
Woe be unto he who builds their filesystems as modules.

Signed-off-by: Jeff Garzik <jeff@garzik.org>
[ Obscure quote from the infamous geek bible? ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-30 22:16:24 -08:00
Jens Axboe
5abc97aa25 [PATCH] splice: add support for SPLICE_F_MOVE flag
This enables the caller to migrate pages from one address space page
cache to another.  In buzz word marketing, you can do zero-copy file
copies!

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-30 12:28:18 -08:00
Jens Axboe
5274f052e7 [PATCH] Introduce sys_splice() system call
This adds support for the sys_splice system call. Using a pipe as a
transport, it can connect to files or sockets (latter as output only).

From the splice.c comments:

   "splice": joining two ropes together by interweaving their strands.

   This is the "extended pipe" functionality, where a pipe is used as
   an arbitrary in-memory buffer. Think of a pipe as a small kernel
   buffer that you can use to transfer data from one end to the other.

   The traditional unix read/write is extended with a "splice()" operation
   that transfers data buffers to or from a pipe buffer.

   Named by Larry McVoy, original implementation from Linus, extended by
   Jens to support splicing to files and fixing the initial implementation
   bugs.

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-30 12:28:18 -08:00