From 4cfb44df8d12a5fc2b801d18dc41b03bf7e6cd7b Mon Sep 17 00:00:00 2001 From: Benjamin Berg Date: Wed, 18 Oct 2023 14:36:42 +0200 Subject: [PATCH] um: chan_user: retry partial writes In the next commit, we are going to set the output FD to be blocking. Once that is done, the write() may be short if an interrupt happens while it is writing out data. As such, to properly catch an EINTR error, we need to retry the write. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20231018123643.1255813-3-benjamin@sipsolutions.net Signed-off-by: Johannes Berg --- arch/um/drivers/chan_user.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c index 60fcb181835d..a66e556012c4 100644 --- a/arch/um/drivers/chan_user.c +++ b/arch/um/drivers/chan_user.c @@ -37,11 +37,23 @@ int generic_read(int fd, __u8 *c_out, void *unused) int generic_write(int fd, const __u8 *buf, size_t n, void *unused) { + int written = 0; int err; - CATCH_EINTR(err = write(fd, buf, n)); - if (err > 0) - return err; + /* The FD may be in blocking mode, as such, need to retry short writes, + * they may have been interrupted by a signal. + */ + do { + errno = 0; + err = write(fd, buf + written, n - written); + if (err > 0) { + written += err; + continue; + } + } while (err < 0 && errno == EINTR); + + if (written > 0) + return written; else if (errno == EAGAIN) return 0; else if (err == 0)