linux.git/fs/splice.c, branch v2.6.31

splice: fix kmaps in default_file_splice_write()

2009-05-19T09:37:46+00:00

Unfortunately multiple kmap() within a single thread are deadlockable,
so writing out multiple buffers with writev() isn't possible.

Change the implementation so that it does a separate write() for each
buffer.  This actually simplifies the code a lot since the
splice_from_pipe() helper can be used.

This limitation is caused by HIGHMEM pages, and so only affects a
subset of architectures and configurations.  In the future it may be
worth to implement default_file_splice_write() in a more efficient way
on configs that allow it.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Jens Axboe

splice: fix error return code

2009-05-14T07:49:44+00:00

fs/splice.c: In function 'default_file_splice_read':
fs/splice.c:566: warning: 'error' may be used uninitialized in this function

which is sort-of true.  The code will in fact return -ENOMEM instead of the
kernel_readv() return value.

Cc: Miklos Szeredi 
Signed-off-by: Andrew Morton 
Signed-off-by: Jens Axboe

splice: fix repeated kmap()'s in default_file_splice_read()

2009-05-13T06:35:35+00:00

We cannot reliably map more than one page at the time, or we risk
deadlocking. Just allocate the pages from low mem instead.

Reported-by: Andrew Morton 
Signed-off-by: Jens Axboe

splice: implement default splice_write method

2009-05-11T12:13:10+00:00

If f_op->splice_write() is not implemented, fall back to a plain write.
Use vfs_writev() to write from the pipe buffers.

This will allow splice on all filesystems and file types.  This
includes "direct_io" files in fuse which bypass the page cache.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Jens Axboe

splice: implement default splice_read method

2009-05-11T12:13:10+00:00

If f_op->splice_read() is not implemented, fall back to a plain read.
Use vfs_readv() to read into previously allocated pages.

This will allow splice and functions using splice, such as the loop
device, to work on all filesystems.  This includes "direct_io" files
in fuse which bypass the page cache.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Jens Axboe

splice: implement pipe to pipe splicing

2009-05-11T12:13:09+00:00

Allow splice(2) to work when both the input and the output is a pipe.

Based on the impementation of the tee(2) syscall, but instead of
duplicating the buffer references move the buffers from the input pipe
to the output pipe.

Moving the whole buffer only succeeds if the full length of the buffer
is spliced.  Otherwise duplicate the buffer, just like tee(2), set the
length of the output buffer and advance the offset on the input
buffer.

Since splice is operating on two pipes, special care needs to be taken
with locking to prevent AN ABBA deadlock.  Again this is done
similarly to the tee(2) syscall, first preparing the input and output
pipes so there's data to consume and space for that data, and then
doing the move operation while holding both locks.

If other processes are doing I/O on the same pipes parallel to the
splice, then by the time both inodes are locked there might be no
buffers left to move, or no space to move them to.  In this case retry
the whole operation, including the preparation phase.  This could lead
to starvation, but I'm not sure if that's serious enough to worry
about.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Jens Axboe

splice: fix new kernel-doc warnings

2009-04-17T14:38:07+00:00

splice: fix kernel-doc warnings

  Warning(fs/splice.c:617): bad line:
  Warning(fs/splice.c:722): No description found for parameter 'sd'
  Warning(fs/splice.c:722): Excess function parameter 'pipe' description in 'splice_from_pipe_begin'

Signed-off-by: Randy Dunlap 
Signed-off-by: Linus Torvalds

splice: add helpers for locking pipe inode

2009-04-15T10:10:12+00:00

There are lots of sequences like this, especially in splice code:

	if (pipe->inode)
		mutex_lock(&pipe->inode->i_mutex);
	/* do something */
	if (pipe->inode)
		mutex_unlock(&pipe->inode->i_mutex);

so introduce helpers which do the conditional locking and unlocking.
Also replace the inode_double_lock() call with a pipe_double_lock()
helper to avoid spreading the use of this functionality beyond the
pipe code.

This patch is just a cleanup, and should cause no behavioral changes.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Jens Axboe

splice: remove generic_file_splice_write_nolock()

2009-04-15T10:10:12+00:00

Remove the now unused generic_file_splice_write_nolock() function.
It's conceptually broken anyway, because splice may need to wait for
pipe events so holding locks across the whole operation is wrong.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Jens Axboe

ocfs2: fix i_mutex locking in ocfs2_splice_to_file()

2009-04-15T10:10:12+00:00

Rearrange locking of i_mutex on destination and call to
ocfs2_rw_lock() so locks are only held while buffers are copied with
the pipe_to_file() actor, and not while waiting for more data on the
pipe.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Jens Axboe