[PATCH 3/3] signalfd: convert to ->read_iter()

Jens Axboe
2024-04-03T14:04:56Z

Rather than use the older style ->read() hook, use ->read_iter() so that
signalfd can support both O_NONBLOCK and IOCB_NOWAIT for non-blocking
read attempts.

Split the fd setup into two parts, so that signalfd can mark the file
mode with FMODE_NOWAIT before installing it into the process table.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
fs/signalfd.c | 46 ++++++++++++++++++++++++++++------------------
1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/fs/signalfd.c b/fs/signalfd.c
index e20d1484c663..72b6796a9a40 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -68,8 +68,7 @@ static __poll_t signalfd_poll(struct file *file, poll_table *wait)
/*
* Copied from copy_siginfo_to_user() in kernel/signal.c
*/
-static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
- kernel_siginfo_t const *kinfo)
+static int signalfd_copyinfo(struct iov_iter *to, kernel_siginfo_t const *kinfo)
{
struct signalfd_siginfo new;

@@ -146,10 +145,7 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
break;
}

- if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))
- return -EFAULT;
-
- return sizeof(*uinfo);
+ return copy_to_iter(&new, sizeof(struct signalfd_siginfo), to);
}

static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info,
@@ -199,28 +195,27 @@ static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info
* error code. The "count" parameter must be at least the size of a
* "struct signalfd_siginfo".
*/
-static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
- loff_t *ppos)
+static ssize_t signalfd_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
+ struct file *file = iocb->ki_filp;
struct signalfd_ctx *ctx = file->private_data;
- struct signalfd_siginfo __user *siginfo;
- int nonblock = file->f_flags & O_NONBLOCK;
+ size_t count = iov_iter_count(to);
ssize_t ret, total = 0;
kernel_siginfo_t info;
+ bool nonblock;

count /= sizeof(struct signalfd_siginfo);
if (!count)
return -EINVAL;

- siginfo = (struct signalfd_siginfo __user *) buf;
+ nonblock = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT;
do {
ret = signalfd_dequeue(ctx, &info, nonblock);
if (unlikely(ret <= 0))
break;
- ret = signalfd_copyinfo(siginfo, &info);
+ ret = signalfd_copyinfo(to, &info);
if (ret < 0)
break;
- siginfo++;
total += ret;
nonblock = 1;
} while (--count);
@@ -246,7 +241,7 @@ static const struct file_operations signalfd_fops = {
#endif
.release = signalfd_release,
.poll = signalfd_poll,
- .read = signalfd_read,
+ .read_iter = signalfd_read_iter,
.llseek = noop_llseek,
};

@@ -265,20 +260,35 @@ static int do_signalfd4(int ufd, sigset_t *mask, int flags)
signotset(mask);

if (ufd == -1) {
+ struct file *file;
+
ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return -ENOMEM;

ctx->sigmask = *mask;

+ ufd = get_unused_fd_flags(O_RDWR |
+ (flags & (O_CLOEXEC | O_NONBLOCK)));
+ if (ufd < 0) {
+ kfree(ctx);
+ return ufd;
+ }
+
+ file = anon_inode_getfile("[signalfd]", &signalfd_fops, ctx,
+ O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
+ if (IS_ERR(file)) {
+ put_unused_fd(ufd);
+ kfree(ctx);
+ return ufd;
+ }
+ file->f_mode |= FMODE_NOWAIT;
+
/*
* When we call this, the initialization must be complete, since
* anon_inode_getfd() will install the fd.
*/
- ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
- O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
- if (ufd < 0)
- kfree(ctx);
+ fd_install(ufd, file);
} else {
struct fd f = fdget(ufd);
if (!f.file)
--
2.43.0