Date: Tue, 31 Jan 2012 03:58:26 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r230803 - in head/sys: fs/nfsclient nfsclient Message-ID: <201201310358.q0V3wQDt017269@svn.freebsd.org>
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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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