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From 0111d01afe82c46656a40269bf21eb7702c02a09 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 16 Jul 2021 16:51:29 -0400
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Subject: [PATCH 13/43] file-posix: fix max_iov for /dev/sg devices
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RH-Author: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Bugzilla: 1957194
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Even though it was only called for devices that have bs->sg set (which
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must be character devices), sg_get_max_segments looked at /sys/dev/block
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which only works for block devices.
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On Linux the sg driver has its own way to provide the maximum number of
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iovecs in a scatter/gather list, so add support for it. The block device
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path is kept because it will be reinstated in the next patches.
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit 8ad5ab6148dca8aad297c134c09c84b0b92d45ed)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/file-posix.c | 11 +++++++++++
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1 file changed, 11 insertions(+)
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diff --git a/block/file-posix.c b/block/file-posix.c
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index 20e14f8e96..74d4903dc1 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -1204,6 +1204,17 @@ static int sg_get_max_segments(int fd)
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goto out;
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}
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+ if (S_ISCHR(st.st_mode)) {
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+ if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) {
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+ return ret;
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+ }
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+ return -ENOTSUP;
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+ }
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+
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+ if (!S_ISBLK(st.st_mode)) {
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+ return -ENOTSUP;
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+ }
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+
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sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments",
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major(st.st_rdev), minor(st.st_rdev));
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sysfd = open(sysfspath, O_RDONLY);
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--
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2.27.0
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