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When a "mount -u" switches an NFS mount point from TCP to UDP,

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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
This commit is contained in:
Rick Macklem 2012-01-31 03:58:26 +00:00
parent a8122d16b5
commit 87b633678b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=230803
2 changed files with 27 additions and 0 deletions
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13
sys/fs/nfsclient/nfs_clvfsops.c
View File

@ -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

14
sys/nfsclient/nfs_vfsops.c
View File

@ -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