From 91885258e8343bb65c08f668d7e6c16563eb4284 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Fri, 19 Mar 2010 08:06:28 -0400 Subject: [PATCH] nfsd: don't break lease while servicing a COMMIT This is the second attempt to fix the problem whereby a COMMIT call causes a lease break and triggers a possible deadlock. The problem is that nfsd attempts to break a lease on a COMMIT call. This triggers a delegation recall if the lease is held for a delegation. If the client is the one holding the delegation and it's the same one on which it's issuing the COMMIT, then it can't return that delegation until the COMMIT is complete. But, nfsd won't complete the COMMIT until the delegation is returned. The client and server are essentially deadlocked until the state is marked bad (due to the client not responding on the callback channel). The first patch attempted to deal with this by eliminating the open of the file altogether and simply had nfsd_commit pass a NULL file pointer to the vfs_fsync_range. That would conflict with some work in progress by Christoph Hellwig to clean up the fsync interface, so this patch takes a different approach. This declares a new NFSD_MAY_NOT_BREAK_LEASE access flag that indicates to nfsd_open that it should not break any leases when opening the file, and has nfsd_commit set that flag on the nfsd_open call. For now, this patch leaves nfsd_commit opening the file with write access since I'm not clear on what sort of access would be more appropriate. Signed-off-by: Jeff Layton Cc: stable@kernel.org Signed-off-by: J. Bruce Fields --- fs/nfsd/vfs.c | 8 +++++--- fs/nfsd/vfs.h | 1 + 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index a11b0e8678ee..c2dcb4c2b1fc 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -723,7 +723,7 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, struct inode *inode; int flags = O_RDONLY|O_LARGEFILE; __be32 err; - int host_err; + int host_err = 0; validate_process_creds(); @@ -760,7 +760,8 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, * Check to see if there are any leases on this file. * This may block while leases are broken. */ - host_err = break_lease(inode, O_NONBLOCK | ((access & NFSD_MAY_WRITE) ? O_WRONLY : 0)); + if (!(access & NFSD_MAY_NOT_BREAK_LEASE)) + host_err = break_lease(inode, O_NONBLOCK | ((access & NFSD_MAY_WRITE) ? O_WRONLY : 0)); if (host_err == -EWOULDBLOCK) host_err = -ETIMEDOUT; if (host_err) /* NOMEM or WOULDBLOCK */ @@ -1168,7 +1169,8 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp, goto out; } - err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_WRITE, &file); + err = nfsd_open(rqstp, fhp, S_IFREG, + NFSD_MAY_WRITE|NFSD_MAY_NOT_BREAK_LEASE, &file); if (err) goto out; if (EX_ISSYNC(fhp->fh_export)) { diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h index 4b1de0a9ea75..217a62c2a357 100644 --- a/fs/nfsd/vfs.h +++ b/fs/nfsd/vfs.h @@ -20,6 +20,7 @@ #define NFSD_MAY_OWNER_OVERRIDE 64 #define NFSD_MAY_LOCAL_ACCESS 128 /* IRIX doing local access check on device special file*/ #define NFSD_MAY_BYPASS_GSS_ON_ROOT 256 +#define NFSD_MAY_NOT_BREAK_LEASE 512 #define NFSD_MAY_CREATE (NFSD_MAY_EXEC|NFSD_MAY_WRITE) #define NFSD_MAY_REMOVE (NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)