From 99c147e2f53726290bbdde795b6efbb4d9138657 Mon Sep 17 00:00:00 2001 From: Fabiano Rosas Date: Mon, 17 Jun 2024 15:57:29 -0300 Subject: [PATCH] monitor: fdset: Match against O_DIRECT We're about to enable the use of O_DIRECT in the migration code and due to the alignment restrictions imposed by filesystems we need to make sure the flag is only used when doing aligned IO. The migration will do parallel IO to different regions of a file, so we need to use more than one file descriptor. Those cannot be obtained by duplicating (dup()) since duplicated file descriptors share the file status flags, including O_DIRECT. If one migration channel does unaligned IO while another sets O_DIRECT to do aligned IO, the filesystem would fail the unaligned operation. The add-fd QMP command along with the fdset code are specifically designed to allow the user to pass a set of file descriptors with different access flags into QEMU to be later fetched by code that needs to alternate between those flags when doing IO. Extend the fdset matching to behave the same with the O_DIRECT flag. Reviewed-by: Peter Xu Signed-off-by: Fabiano Rosas --- monitor/fds.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/monitor/fds.c b/monitor/fds.c index d8c6b395b0..b5416b5b5d 100644 --- a/monitor/fds.c +++ b/monitor/fds.c @@ -424,6 +424,11 @@ int monitor_fdset_dup_fd_add(int64_t fdset_id, int flags, Error **errp) int fd = -1; int dup_fd; int mon_fd_flags; + int mask = O_ACCMODE; + +#ifdef O_DIRECT + mask |= O_DIRECT; +#endif if (mon_fdset->id != fdset_id) { continue; @@ -437,7 +442,7 @@ int monitor_fdset_dup_fd_add(int64_t fdset_id, int flags, Error **errp) return -1; } - if ((flags & O_ACCMODE) == (mon_fd_flags & O_ACCMODE)) { + if ((flags & mask) == (mon_fd_flags & mask)) { fd = mon_fdset_fd->fd; break; }