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relay: make create_buf_file and remove_buf_file callbacks mandatory 

All clients provide create_buf_file and remove_buf_file callbacks, and
they're required for relay to make sense.  There is no point in them being
optional.

Also document whether each callback is mandatory/optional.

Link: https://lkml.kernel.org/r/88003c1527386b93036e286e7917f1e33aec84ac.1606153547.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jani Nikula 2020-12-15 20:45:53 -08:00 committed by Linus Torvalds
parent 6f8f25440d
commit 371e03880d
2 changed files with 7 additions and 25 deletions
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6
include/linux/relay.h
View File

@ -89,6 +89,8 @@ struct rchan_callbacks
* The client should return 1 to continue logging, 0 to stop
* logging.
*
* This callback is optional.
*
* NOTE: subbuf_start will also be invoked when the buffer is
* created, so that the first sub-buffer can be initialized
* if necessary. In this case, prev_subbuf will be NULL.
@ -122,6 +124,8 @@ struct rchan_callbacks
* cause relay_open() to create a single global buffer rather
* than the default set of per-cpu buffers.
*
* This callback is mandatory.
*
* See Documentation/filesystems/relay.rst for more info.
*/
struct dentry *(*create_buf_file)(const char *filename,
@ -139,6 +143,8 @@ struct rchan_callbacks
* channel buffer.
*
* The callback should return 0 if successful, negative if not.
*
* This callback is mandatory.
*/
int (*remove_buf_file)(struct dentry *dentry);
};

26
kernel/relay.c
View File

@ -271,26 +271,6 @@ static int subbuf_start_default_callback (struct rchan_buf *buf,
return 1;
}
/*
* create_buf_file_create() default callback. Does nothing.
*/
static struct dentry *create_buf_file_default_callback(const char *filename,
struct dentry *parent,
umode_t mode,
struct rchan_buf *buf,
int *is_global)
{
return NULL;
}
/*
* remove_buf_file() default callback. Does nothing.
*/
static int remove_buf_file_default_callback(struct dentry *dentry)
{
return -EINVAL;
}
/**
* wakeup_readers - wake up readers waiting on a channel
* @work: contains the channel buffer
@ -467,10 +447,6 @@ static void setup_callbacks(struct rchan *chan,
{
if (!cb->subbuf_start)
cb->subbuf_start = subbuf_start_default_callback;
if (!cb->create_buf_file)
cb->create_buf_file = create_buf_file_default_callback;
if (!cb->remove_buf_file)
cb->remove_buf_file = remove_buf_file_default_callback;
chan->cb = cb;
}
@ -530,7 +506,7 @@ struct rchan *relay_open(const char *base_filename,
return NULL;
if (subbuf_size > UINT_MAX / n_subbufs)
return NULL;
if (!cb)
if (!cb || !cb->create_buf_file || !cb->remove_buf_file)
return NULL;
chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);