Date: Wed, 10 Jul 2013 00:31:29 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r253124 - stable/9/sys/fs/nfsclient Message-ID: <201307100031.r6A0VTLC006222@svn.freebsd.org>
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Author: rmacklem Date: Wed Jul 10 00:31:28 2013 New Revision: 253124 URL: http://svnweb.freebsd.org/changeset/base/253124 Log: MFC: r252528 A problem with the old NFS client where large writes to large files would sometimes result in a corrupted file was reported via email. This problem appears to have been caused by r251719 (reverting r251719 fixed the problem). Although I have not been able to reproduce this problem, I suspect it is caused by another thread increasing np->n_size after the mtx_unlock(&np->n_mtx) but before the vnode_pager_setsize() call. Since the np->n_mtx mutex serializes updates to np->n_size, doing the vnode_pager_setsize() with the mutex locked appears to avoid the problem. Unfortunately, vnode_pager_setsize() where the new size is smaller, cannot be called with a mutex held. This patch returns the semantics to be close to pre-r251719 (actually pre-r248567, r248581, r248567 for the new client) such that the call to vnode_pager_setsize() is only delayed until after the mutex is unlocked when np->n_size is shrinking. Since the file is growing when being written, I believe this will fix the corruption. A better solution might be to replace the mutex with a sleep lock, but that is a non-trivial conversion, so this fix is hoped to be sufficient in the meantime. Tested by: remy.nonnenmacher@activnetworks.com Modified: stable/9/sys/fs/nfsclient/nfs_clport.c Directory Properties: stable/9/sys/ (props changed) stable/9/sys/fs/ (props changed) Modified: stable/9/sys/fs/nfsclient/nfs_clport.c ============================================================================== --- stable/9/sys/fs/nfsclient/nfs_clport.c Tue Jul 9 23:54:43 2013 (r253123) +++ stable/9/sys/fs/nfsclient/nfs_clport.c Wed Jul 10 00:31:28 2013 (r253124) @@ -439,6 +439,7 @@ nfscl_loadattrcache(struct vnode **vpp, vap->va_size = np->n_size; np->n_attrstamp = 0; KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp); + vnode_pager_setsize(vp, np->n_size); } else if (np->n_flag & NMODIFIED) { /* * We've modified the file: Use the larger @@ -450,12 +451,22 @@ nfscl_loadattrcache(struct vnode **vpp, np->n_size = vap->va_size; np->n_flag |= NSIZECHANGED; } + vnode_pager_setsize(vp, np->n_size); + } else if (vap->va_size < np->n_size) { + /* + * When shrinking the size, the call to + * vnode_pager_setsize() cannot be done + * with the mutex held, so delay it until + * after the mtx_unlock call. + */ + nsize = np->n_size = vap->va_size; + np->n_flag |= NSIZECHANGED; + setnsize = 1; } else { np->n_size = vap->va_size; np->n_flag |= NSIZECHANGED; + vnode_pager_setsize(vp, np->n_size); } - setnsize = 1; - nsize = vap->va_size; } else { np->n_size = vap->va_size; }
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