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bcachefs: Thread with file documentation

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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-02-03 15:43:16 -05:00
parent f704f108af
commit 032b3fd057
2 changed files with 40 additions and 7 deletions
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15
fs/bcachefs/thread_with_file.c
View file

@ -76,16 +76,16 @@ static bool stdio_redirect_has_output(struct stdio_redirect *stdio)
return stdio->output.buf.nr || stdio->done;
}
#define WRITE_BUFFER 4096
#define STDIO_REDIRECT_BUFSIZE 4096
static bool stdio_redirect_has_input_space(struct stdio_redirect *stdio)
{
return stdio->input.buf.nr < WRITE_BUFFER || stdio->done;
return stdio->input.buf.nr < STDIO_REDIRECT_BUFSIZE || stdio->done;
}
static bool stdio_redirect_has_output_space(struct stdio_redirect *stdio)
{
return stdio->output.buf.nr < WRITE_BUFFER || stdio->done;
return stdio->output.buf.nr < STDIO_REDIRECT_BUFSIZE || stdio->done;
}
static void stdio_buf_init(struct stdio_buf *buf)
@ -171,11 +171,12 @@ static ssize_t thread_with_stdio_write(struct file *file, const char __user *ubu
}
spin_lock(&buf->lock);
if (buf->buf.nr < WRITE_BUFFER)
darray_make_room_gfp(&buf->buf, min(b, WRITE_BUFFER - buf->buf.nr), __GFP_NOWARN);
if (buf->buf.nr < STDIO_REDIRECT_BUFSIZE)
darray_make_room_gfp(&buf->buf,
min(b, STDIO_REDIRECT_BUFSIZE - buf->buf.nr), GFP_NOWAIT);
b = min(len, darray_room(buf->buf));
if (b && !copy_from_user_nofault(&buf->buf.data[buf->buf.nr], ubuf, b)) {
if (b && !copy_from_user_nofault(&darray_top(buf->buf), ubuf, b)) {
buf->buf.nr += b;
ubuf += b;
len -= b;
@ -338,7 +339,7 @@ void bch2_stdio_redirect_vprintf(struct stdio_redirect *stdio, bool nonblocking,
return;
spin_lock_irqsave(&buf->lock, flags);
bch2_darray_vprintf(&buf->buf, nonblocking ? __GFP_NOWARN : GFP_KERNEL, fmt, args);
bch2_darray_vprintf(&buf->buf, nonblocking ? GFP_NOWAIT : GFP_KERNEL, fmt, args);
spin_unlock_irqrestore(&buf->lock, flags);
wake_up(&buf->wait);

32
fs/bcachefs/thread_with_file.h
View file

@ -4,6 +4,38 @@
#include "thread_with_file_types.h"
/*
* Thread with file: Run a kthread and connect it to a file descriptor, so that
* it can be interacted with via fd read/write methods and closing the file
* descriptor stops the kthread.
*
* We have two different APIs:
*
* thread_with_file, the low level version.
* You get to define the full file_operations, including your release function,
* which means that you must call bch2_thread_with_file_exit() from your
* .release method
*
* thread_with_stdio, the higher level version
* This implements full piping of input and output, including .poll.
*
* Notes on behaviour:
* - kthread shutdown behaves like writing or reading from a pipe that has been
* closed
* - Input and output buffers are 4096 bytes, although buffers may in some
* situations slightly exceed that limit so as to avoid chopping off a
* message in the middle in nonblocking mode.
* - Input/output buffers are lazily allocated, with GFP_NOWAIT allocations -
* should be fine but might change in future revisions.
* - Output buffer may grow past 4096 bytes to deal with messages that are
* bigger than 4096 bytes
* - Writing may be done blocking or nonblocking; in nonblocking mode, we only
* drop entire messages.
*
* To write, use stdio_redirect_printf()
* To read, use stdio_redirect_read() or stdio_redirect_readline()
*/
struct task_struct;
struct thread_with_file {