bcachefs: thread_with_file: allow creation of readonly files

Create a new run_thread_with_stdout function that opens a file in
O_RDONLY mode so that the kernel can write things to userspace but
userspace cannot write to the kernel.  This will be used to convey xfs
health event information to userspace.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/thread_with_file.c b/fs/bcachefs/thread_with_file.c
index 96ac2b2c60e122a09e7e18e872e3e5da6aa1c06c..d1cd5f4ab06edeb8286ce6039e331b65e17a47a9 100644 (file)
--- a/fs/bcachefs/thread_with_file.c
+++ b/fs/bcachefs/thread_with_file.c
@@ -231,6 +231,22 @@ static __poll_t thread_with_stdio_poll(struct file *file, struct poll_table_stru
        return mask;
 }
 
+static __poll_t thread_with_stdout_poll(struct file *file, struct poll_table_struct *wait)
+{
+       struct thread_with_stdio *thr =
+               container_of(file->private_data, struct thread_with_stdio, thr);
+
+       poll_wait(file, &thr->stdio.output.wait, wait);
+
+       __poll_t mask = 0;
+
+       if (stdio_redirect_has_output(&thr->stdio))
+               mask |= EPOLLIN;
+       if (thr->thr.done)
+               mask |= EPOLLHUP|EPOLLERR;
+       return mask;
+}
+
 static const struct file_operations thread_with_stdio_fops = {
        .llseek         = no_llseek,
        .read           = thread_with_stdio_read,
@@ -239,6 +255,13 @@ static const struct file_operations thread_with_stdio_fops = {
        .release        = thread_with_stdio_release,
 };
 
+static const struct file_operations thread_with_stdout_fops = {
+       .llseek         = no_llseek,
+       .read           = thread_with_stdio_read,
+       .poll           = thread_with_stdout_poll,
+       .release        = thread_with_stdio_release,
+};
+
 static int thread_with_stdio_fn(void *arg)
 {
        struct thread_with_stdio *thr = arg;
@@ -261,6 +284,19 @@ int bch2_run_thread_with_stdio(struct thread_with_stdio *thr,
        return bch2_run_thread_with_file(&thr->thr, &thread_with_stdio_fops, thread_with_stdio_fn);
 }
 
+int bch2_run_thread_with_stdout(struct thread_with_stdio *thr,
+                               void (*exit)(struct thread_with_stdio *),
+                               void (*fn)(struct thread_with_stdio *))
+{
+       stdio_buf_init(&thr->stdio.input);
+       stdio_buf_init(&thr->stdio.output);
+       thr->exit       = exit;
+       thr->fn         = fn;
+
+       return bch2_run_thread_with_file(&thr->thr, &thread_with_stdout_fops, thread_with_stdio_fn);
+}
+EXPORT_SYMBOL_GPL(bch2_run_thread_with_stdout);
+
 int bch2_stdio_redirect_read(struct stdio_redirect *stdio, char *ubuf, size_t len)
 {
        struct stdio_buf *buf = &stdio->input;

diff --git a/fs/bcachefs/thread_with_file.h b/fs/bcachefs/thread_with_file.h
index f06f8ff19a790a5f398a05d7389da9b87827b0b5..2b687723d6b9b78f3d07e93c2042d2b213e5482a 100644 (file)
--- a/fs/bcachefs/thread_with_file.h
+++ b/fs/bcachefs/thread_with_file.h
@@ -59,6 +59,9 @@ struct thread_with_stdio {
 int bch2_run_thread_with_stdio(struct thread_with_stdio *,
                               void (*exit)(struct thread_with_stdio *),
                               void (*fn)(struct thread_with_stdio *));
+int bch2_run_thread_with_stdout(struct thread_with_stdio *,
+                               void (*exit)(struct thread_with_stdio *),
+                               void (*fn)(struct thread_with_stdio *));
 int bch2_stdio_redirect_read(struct stdio_redirect *, char *, size_t);
 int bch2_stdio_redirect_readline(struct stdio_redirect *, char *, size_t);