5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: John Keeping <john@xxxxxxxxxxxx> [ Upstream commit 2972e3050e3517a85ca1813b227d4c302e804343 ] The tracing marker files are write-only streams with no meaningful concept of file position. Using stream_open() to mark them as stream-link indicates this and has the added advantage that a single file descriptor can now be used from multiple threads without contention thanks to clearing FMODE_ATOMIC_POS. Note that this has the potential to break existing userspace by since both lseek(2) and pwrite(2) will now return ESPIPE when previously lseek would have updated the stored offset and pwrite would have appended to the trace. A survey of libtracefs and several other projects found to use trace_marker(_raw) [1][2][3] suggests that everyone limits themselves to calling write(2) and close(2) on these file descriptors so there is a good chance this will go unnoticed and the benefits of reduced overhead and lock contention seem worth the risk. [1] https://github.com/google/perfetto [2] https://github.com/intel/media-driver/ [3] https://w1.fi/cgit/hostap/ Link: https://lkml.kernel.org/r/20211207142558.347029-1-john@xxxxxxxxxxxx Signed-off-by: John Keeping <john@xxxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Stable-dep-of: f5ca233e2e66 ("tracing: Increase trace array ref count on enable and filter files") Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/trace/trace.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 6adacfc880d6c..5aa23a4382c5e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4887,6 +4887,12 @@ int tracing_open_generic_tr(struct inode *inode, struct file *filp) return 0; } +static int tracing_mark_open(struct inode *inode, struct file *filp) +{ + stream_open(inode, filp); + return tracing_open_generic_tr(inode, filp); +} + static int tracing_release(struct inode *inode, struct file *file) { struct trace_array *tr = inode->i_private; @@ -7225,9 +7231,6 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if (tt) event_triggers_post_call(tr->trace_marker_file, tt); - if (written > 0) - *fpos += written; - return written; } @@ -7286,9 +7289,6 @@ tracing_mark_raw_write(struct file *filp, const char __user *ubuf, __buffer_unlock_commit(buffer, event); - if (written > 0) - *fpos += written; - return written; } @@ -7699,16 +7699,14 @@ static const struct file_operations tracing_free_buffer_fops = { }; static const struct file_operations tracing_mark_fops = { - .open = tracing_open_generic_tr, + .open = tracing_mark_open, .write = tracing_mark_write, - .llseek = generic_file_llseek, .release = tracing_release_generic_tr, }; static const struct file_operations tracing_mark_raw_fops = { - .open = tracing_open_generic_tr, + .open = tracing_mark_open, .write = tracing_mark_raw_write, - .llseek = generic_file_llseek, .release = tracing_release_generic_tr, }; -- 2.40.1
