From 8ad5ab6148dca8aad297c134c09c84b0b92d45ed Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 15 Apr 2021 12:41:31 +0200 Subject: [PATCH] file-posix: fix max_iov for /dev/sg devices Even though it was only called for devices that have bs->sg set (which must be character devices), sg_get_max_segments looked at /sys/dev/block which only works for block devices. On Linux the sg driver has its own way to provide the maximum number of iovecs in a scatter/gather list, so add support for it. The block device path is kept because it will be reinstated in the next patches. Signed-off-by: Paolo Bonzini Reviewed-by: Max Reitz --- block/file-posix.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/block/file-posix.c b/block/file-posix.c index b3fbb9bd63..b8dc19ce1a 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1178,6 +1178,17 @@ static int sg_get_max_segments(int fd) goto out; } + if (S_ISCHR(st.st_mode)) { + if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) { + return ret; + } + return -ENOTSUP; + } + + if (!S_ISBLK(st.st_mode)) { + return -ENOTSUP; + } + sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments", major(st.st_rdev), minor(st.st_rdev)); sysfd = open(sysfspath, O_RDONLY); -- 2.30.2