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From: Vivek Goyal <vgoyal@redhat.com>
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Date: Mon, 27 Jan 2020 19:02:14 +0000
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Subject: [PATCH] virtiofsd: Reset O_DIRECT flag during file open
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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If an application wants to do direct IO and opens a file with O_DIRECT
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in guest, that does not necessarily mean that we need to bypass page
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cache on host as well. So reset this flag on host.
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If somebody needs to bypass page cache on host as well (and it is safe to
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do so), we can add a knob in daemon later to control this behavior.
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I check virtio-9p and they do reset O_DIRECT flag.
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Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
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Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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(cherry picked from commit 65da4539803373ec4eec97ffc49ee90083e56efd)
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---
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tools/virtiofsd/passthrough_ll.c | 14 ++++++++++++++
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1 file changed, 14 insertions(+)
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diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
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index ccbbec18b0..948cb19c77 100644
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--- a/tools/virtiofsd/passthrough_ll.c
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+++ b/tools/virtiofsd/passthrough_ll.c
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@@ -1721,6 +1721,13 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
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goto out;
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}
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+ /*
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+ * O_DIRECT in guest should not necessarily mean bypassing page
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+ * cache on host as well. If somebody needs that behavior, it
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+ * probably should be a configuration knob in daemon.
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+ */
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+ fi->flags &= ~O_DIRECT;
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+
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fd = openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOLLOW,
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mode);
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err = fd == -1 ? errno : 0;
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@@ -1950,6 +1957,13 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
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fi->flags &= ~O_APPEND;
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}
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+ /*
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+ * O_DIRECT in guest should not necessarily mean bypassing page
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+ * cache on host as well. If somebody needs that behavior, it
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+ * probably should be a configuration knob in daemon.
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+ */
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+ fi->flags &= ~O_DIRECT;
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+
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sprintf(buf, "%i", lo_fd(req, ino));
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fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
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if (fd == -1) {
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