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relay: allow the use of const callback structs

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None of the relay users require the use of mutable structs for callbacks,
however the relay code does.  Instead of assigning the default callback
for subbuf_start, add a wrapper to conditionally call the client callback
if available, and fall back to default behaviour otherwise.

This lets all relay users make their struct rchan_callbacks const data.

[jani.nikula@intel.com: cleanups, per Christoph]
  Link: https://lkml.kernel.org/r/20201124115412.32402-1-jani.nikula@intel.com

Link: https://lkml.kernel.org/r/cc3ff292e4eb4fdc56bee3d690c7b8e39209cd37.1606153547.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
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 20:45:57 -08:00 committed by Linus Torvalds
parent 371e03880d
commit 023542f48b
2 changed files with 12 additions and 29 deletions
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4
include/linux/relay.h
View File

@ -62,7 +62,7 @@ struct rchan
size_t subbuf_size; /* sub-buffer size */
size_t n_subbufs; /* number of sub-buffers per buffer */
size_t alloc_size; /* total buffer size allocated */
struct rchan_callbacks *cb; /* client callbacks */
const struct rchan_callbacks *cb; /* client callbacks */
struct kref kref; /* channel refcount */
void *private_data; /* for user-defined data */
size_t last_toobig; /* tried to log event > subbuf size */
@ -157,7 +157,7 @@ struct rchan *relay_open(const char *base_filename,
struct dentry *parent,
size_t subbuf_size,
size_t n_subbufs,
struct rchan_callbacks *cb,
const struct rchan_callbacks *cb,
void *private_data);
extern int relay_late_setup_files(struct rchan *chan,
const char *base_filename,

37
kernel/relay.c
View File

@ -252,23 +252,14 @@ EXPORT_SYMBOL_GPL(relay_buf_full);
* High-level relay kernel API and associated functions.
*/
/*
* rchan_callback implementations defining default channel behavior. Used
* in place of corresponding NULL values in client callback struct.
*/
/*
* subbuf_start() default callback. Does nothing.
*/
static int subbuf_start_default_callback (struct rchan_buf *buf,
void *subbuf,
void *prev_subbuf,
size_t prev_padding)
static int relay_subbuf_start(struct rchan_buf *buf, void *subbuf,
void *prev_subbuf, size_t prev_padding)
{
if (relay_buf_full(buf))
return 0;
if (!buf->chan->cb->subbuf_start)
return !relay_buf_full(buf);
return 1;
return buf->chan->cb->subbuf_start(buf, subbuf,
prev_subbuf, prev_padding);
}
/**
@ -314,7 +305,7 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
for (i = 0; i < buf->chan->n_subbufs; i++)
buf->padding[i] = 0;
buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
relay_subbuf_start(buf, buf->data, NULL, 0);
}
/**
@ -442,14 +433,6 @@ static void relay_close_buf(struct rchan_buf *buf)
kref_put(&buf->kref, relay_remove_buf);
}
static void setup_callbacks(struct rchan *chan,
struct rchan_callbacks *cb)
{
if (!cb->subbuf_start)
cb->subbuf_start = subbuf_start_default_callback;
chan->cb = cb;
}
int relay_prepare_cpu(unsigned int cpu)
{
struct rchan *chan;
@ -495,7 +478,7 @@ struct rchan *relay_open(const char *base_filename,
struct dentry *parent,
size_t subbuf_size,
size_t n_subbufs,
struct rchan_callbacks *cb,
const struct rchan_callbacks *cb,
void *private_data)
{
unsigned int i;
@ -529,7 +512,7 @@ struct rchan *relay_open(const char *base_filename,
chan->has_base_filename = 1;
strlcpy(chan->base_filename, base_filename, NAME_MAX);
}
setup_callbacks(chan, cb);
chan->cb = cb;
kref_init(&chan->kref);
mutex_lock(&relay_channels_mutex);
@ -712,7 +695,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
new = buf->start + new_subbuf * buf->chan->subbuf_size;
buf->offset = 0;
if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
if (!relay_subbuf_start(buf, new, old, buf->prev_padding)) {
buf->offset = buf->chan->subbuf_size + 1;
return 0;
}