linux.git/fs/splice.c, branch v2.6.23

Fix possible splice() mmap_sem deadlock

2007-10-01T20:17:28+00:00

Nick Piggin points out that splice isn't being good about the mmap
semaphore: while two readers can nest inside each others, it does leave
a possible deadlock if a writer (ie a new mmap()) comes in during that
nesting.

Original "just move the locking" patch by Nick, replaced by one by me
based on an optimistic pagefault_disable().  And then Jens tested and
updated that patch.

Reported-by: Nick Piggin 
Tested-by: Jens Axboe 
Cc: Andrew Morton 
Signed-off-by: Linus Torvalds

docbook: add pipes, other fixes

2007-07-27T06:08:51+00:00

Fix some typos in pipe.c and splice.c.
Add pipes API to kernel-api.tmpl.

Signed-off-by: Randy Dunlap 
Signed-off-by: Jens Axboe

splice: fix bad unlock_page() in error case

2007-07-20T16:07:01+00:00

If add_to_page_cache_lru() fails, the page will not be locked. But
splice jumps to an error path that does a page release and unlock,
causing a BUG() in unlock_page().

Fix this by adding one more label that just releases the page. This bug
was actually triggered on EL5 by gurudas pai 
using fio.

Signed-off-by: Jens Axboe 
Signed-off-by: Linus Torvalds

readahead: split ondemand readahead interface into two functions

2007-07-19T17:04:44+00:00

Split ondemand readahead interface into two functions.  I think this makes it
a little clearer for non-readahead experts (like Rusty).

Internally they both call ondemand_readahead(), but the page argument is
changed to an obvious boolean flag.

Signed-off-by: Rusty Russell 
Signed-off-by: Fengguang Wu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

readahead: pass real splice size

2007-07-19T17:04:44+00:00

Pass real splice size to page_cache_readahead_ondemand().

The splice code works in chunks of 16 pages internally.  The readahead code
should be told of the overall splice size, instead of the internal chunk size.
 Otherwize bad things may happen.  Imagine some 17-page random splice reads.
The code before this patch will result in two readahead calls: readahead(16);
readahead(1); That leads to one 16-page I/O and one 32-page I/O: one extra I/O
and 31 readahead miss pages.

Signed-off-by: Fengguang Wu 
Cc: Jens Axboe 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

readahead: move synchronous readahead call out of splice loop

2007-07-19T17:04:44+00:00

Move synchronous page_cache_readahead_ondemand() call out of splice loop.

This avoids one pointless page allocation/insertion in case of non-zero
ra_pages, or many pointless readahead calls in case of zero ra_pages.

Note that if a user sets ra_pages to less than PIPE_BUFFERS=16 pages, he will
not get expected readahead behavior anyway.  The splice code works in batches
of 16 pages, which can be taken as another form of synchronous readahead.

Signed-off-by: Fengguang Wu 
Cc: Jens Axboe 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

readahead: convert splice invocations

2007-07-19T17:04:44+00:00

Convert splice reads to use on-demand readahead.

Signed-off-by: Fengguang Wu 
Cc: Steven Pratt 
Cc: Ram Pai 
Cc: Jens Axboe 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

splice: direct splicing updates ppos twice

2007-07-16T13:02:48+00:00

OGAWA Hirofumi  reported that he's noticed
nfsd read corruption in recent kernels, and did the hard work of
discovering that it's due to splice updating the file position twice.
This means that the next operation would start further ahead than it
should.

nfsd_vfs_read()
    splice_direct_to_actor()
        while(len) {
            do_splice_to()                     [update sd->pos]
                -> generic_file_splice_read()  [read from sd->pos]
            nfsd_direct_splice_actor()
                -> __splice_from_pipe()        [update sd->pos]

There's nothing wrong with the core splice code, but the direct
splicing is an addon that calls both input and output paths.
So it has to take care in locally caching offset so it remains correct.

Signed-off-by: Jens Axboe

splice: fix offset mangling with direct splicing (sendfile)

2007-07-13T12:14:31+00:00

If the output actor doesn't transfer the full amount of data, we will
increment ppos too much. Two related bugs in there:

- We need to break out and return actor() retval if it is shorted than
  what we spliced into the pipe.

- Adjust ppos only according to actor() return.

Also fix loop problem in generic_file_splice_read(), it should not keep
going when data has already been transferred.

Signed-off-by: Jens Axboe

security: revalidate rw permissions for sys_splice and sys_vmsplice

2007-07-13T12:14:29+00:00

Revalidate read/write permissions for splice(2) and vmslice(2), in case
security policy has changed since the files were opened.

Acked-by: Stephen Smalley 
Signed-off-by: James Morris 
Signed-off-by: Jens Axboe