Author: rmacklem
Date: Tue Jan 31 03:58:26 2012
New Revision: 230803
URL: http://svn.freebsd.org/changeset/base/230803
Log:
When a "mount -u" switches an NFS mount point from TCP to UDP,
any thread doing an I/O RPC with a transfer size greater than
NFS_UDPMAXDATA will be hung indefinitely, retrying the RPC.
After a discussion on freebsd-fs@, I decided to add a warning
message for this case, as suggested by Jeremy Chadwick.
Suggested by: freebsd at jdc.parodius.com (Jeremy Chadwick)
MFC after: 2 weeks
Modified:
head/sys/fs/nfsclient/nfs_clvfsops.c
head/sys/nfsclient/nfs_vfsops.c
Modified: head/sys/fs/nfsclient/nfs_clvfsops.c
==============================================================================
--- head/sys/fs/nfsclient/nfs_clvfsops.c Tue Jan 31 02:30:47 2012
(r230802)
+++ head/sys/fs/nfsclient/nfs_clvfsops.c Tue Jan 31 03:58:26 2012
(r230803)
@@ -999,6 +999,19 @@ nfs_mount(struct mount *mp)
error = EIO;
goto out;
}
+
+ /*
+ * If a change from TCP->UDP is done and there are thread(s)
+ * that have I/O RPC(s) in progress with a tranfer size
+ * greater than NFS_MAXDGRAMDATA, those thread(s) will be
+ * hung, retrying the RPC(s) forever. Usually these threads
+ * will be seen doing an uninterruptible sleep on wait channel
+ * "newnfsreq" (truncated to "newnfsre" by procstat).
+ */
+ if (args.sotype == SOCK_DGRAM && nmp->nm_sotype == SOCK_STREAM)
+ tprintf(td->td_proc, LOG_WARNING,
+ "Warning: mount -u that changes TCP->UDP can result in hung threads\n");
+
/*
* When doing an update, we can't change version,
* security, switch lockd strategies or change cookie
Modified: head/sys/nfsclient/nfs_vfsops.c
==============================================================================
--- head/sys/nfsclient/nfs_vfsops.c Tue Jan 31 02:30:47 2012
(r230802)
+++ head/sys/nfsclient/nfs_vfsops.c Tue Jan 31 03:58:26 2012
(r230803)
@@ -56,6 +56,7 @@ __FBSDID("$FreeBSD$");
#include <sys/socketvar.h>
#include <sys/sockio.h>
#include <sys/sysctl.h>
+#include <sys/syslog.h>
#include <sys/vnode.h>
#include <sys/signalvar.h>
@@ -1116,6 +1117,19 @@ nfs_mount(struct mount *mp)
error = EIO;
goto out;
}
+
+ /*
+ * If a change from TCP->UDP is done and there are thread(s)
+ * that have I/O RPC(s) in progress with a tranfer size
+ * greater than NFS_MAXDGRAMDATA, those thread(s) will be
+ * hung, retrying the RPC(s) forever. Usually these threads
+ * will be seen doing an uninterruptible sleep on wait channel
+ * "newnfsreq" (truncated to "newnfsre" by procstat).
+ */
+ if (args.sotype == SOCK_DGRAM && nmp->nm_sotype == SOCK_STREAM)
+ tprintf(curthread->td_proc, LOG_WARNING,
+ "Warning: mount -u that changes TCP->UDP can result in hung threads\n");
+
/*
* When doing an update, we can't change from or to
* v3, switch lockd strategies or change cookie translation
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