From 41f53350a0f36a7b8e31bec0d0ca907e028ab4cd Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 24 Jan 2017 09:22:41 +0100 Subject: [PATCH] nfsd: special case truncates some more Both the NFS protocols and the Linux VFS use a setattr operation with a bitmap of attributs to set to set various file attributes including the file size and the uid/gid. The Linux syscalls never mixes size updates with unrelated updates like the uid/gid, and some file systems like XFS and GFS2 rely on the fact that truncates might not update random other attributes, and many other file systems handle the case but do not update the different attributes in the same transaction. NFSD on the other hand passes the attributes it gets on the wire more or less directly through to the VFS, leading to updates the file systems don't expect. XFS at least has an assert on the allowed attributes, which caught an unusual NFS client setting the size and group at the same time. To handle this issue properly this switches nfsd to call vfs_truncate for size changes, and then handle all other attributes through notify_change. As a side effect this also means less boilerplace code around the size change as we can now reuse the VFS code. Signed-off-by: Christoph Hellwig Signed-off-by: J. Bruce Fields --- fs/nfsd/vfs.c | 97 ++++++++++++++++++++------------------------------- 1 file changed, 37 insertions(+), 60 deletions(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 26c6fdb4bf67..ca13236dbb1f 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -332,37 +332,6 @@ nfsd_sanitize_attrs(struct inode *inode, struct iattr *iap) } } -static __be32 -nfsd_get_write_access(struct svc_rqst *rqstp, struct svc_fh *fhp, - struct iattr *iap) -{ - struct inode *inode = d_inode(fhp->fh_dentry); - int host_err; - - if (iap->ia_size < inode->i_size) { - __be32 err; - - err = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry, - NFSD_MAY_TRUNC | NFSD_MAY_OWNER_OVERRIDE); - if (err) - return err; - } - - host_err = get_write_access(inode); - if (host_err) - goto out_nfserrno; - - host_err = locks_verify_truncate(inode, NULL, iap->ia_size); - if (host_err) - goto out_put_write_access; - return 0; - -out_put_write_access: - put_write_access(inode); -out_nfserrno: - return nfserrno(host_err); -} - /* * Set various file attributes. After this call fhp needs an fh_put. */ @@ -377,7 +346,6 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap, __be32 err; int host_err; bool get_write_count; - int size_change = 0; if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME | ATTR_SIZE)) accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE; @@ -390,11 +358,11 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap, /* Get inode */ err = fh_verify(rqstp, fhp, ftype, accmode); if (err) - goto out; + return err; if (get_write_count) { host_err = fh_want_write(fhp); if (host_err) - return nfserrno(host_err); + goto out_host_err; } dentry = fhp->fh_dentry; @@ -405,50 +373,59 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap, iap->ia_valid &= ~ATTR_MODE; if (!iap->ia_valid) - goto out; + return 0; nfsd_sanitize_attrs(inode, iap); + if (check_guard && guardtime != inode->i_ctime.tv_sec) + return nfserr_notsync; + /* * The size case is special, it changes the file in addition to the - * attributes. + * attributes, and file systems don't expect it to be mixed with + * "random" attribute changes. We thus split out the size change + * into a separate call for vfs_truncate, and do the rest as a + * a separate setattr call. */ if (iap->ia_valid & ATTR_SIZE) { - err = nfsd_get_write_access(rqstp, fhp, iap); - if (err) - goto out; - size_change = 1; + struct path path = { + .mnt = fhp->fh_export->ex_path.mnt, + .dentry = dentry, + }; + bool implicit_mtime = false; /* - * RFC5661, Section 18.30.4: - * Changing the size of a file with SETATTR indirectly - * changes the time_modify and change attributes. - * - * (and similar for the older RFCs) + * vfs_truncate implicity updates the mtime IFF the file size + * actually changes. Avoid the additional seattr call below if + * the only other attribute that the client sends is the mtime. */ - if (iap->ia_size != i_size_read(inode)) - iap->ia_valid |= ATTR_MTIME; - } + if (iap->ia_size != i_size_read(inode) && + ((iap->ia_valid & ~(ATTR_SIZE | ATTR_MTIME)) == 0)) + implicit_mtime = true; - iap->ia_valid |= ATTR_CTIME; + host_err = vfs_truncate(&path, iap->ia_size); + if (host_err) + goto out_host_err; - if (check_guard && guardtime != inode->i_ctime.tv_sec) { - err = nfserr_notsync; - goto out_put_write_access; + iap->ia_valid &= ~ATTR_SIZE; + if (implicit_mtime) + iap->ia_valid &= ~ATTR_MTIME; + if (!iap->ia_valid) + goto done; } + iap->ia_valid |= ATTR_CTIME; + fh_lock(fhp); host_err = notify_change(dentry, iap, NULL); fh_unlock(fhp); - err = nfserrno(host_err); + if (host_err) + goto out_host_err; -out_put_write_access: - if (size_change) - put_write_access(inode); - if (!err) - err = nfserrno(commit_metadata(fhp)); -out: - return err; +done: + host_err = commit_metadata(fhp); +out_host_err: + return nfserrno(host_err); } #if defined(CONFIG_NFSD_V4) -- 2.20.1