NFS: Remove BKL requirement from attribute updates

The main problem is dealing with inode->i_size: we need to set the
inode->i_lock on all attribute updates, and so vmtruncate won't cut it.
Make an NFS-private version of vmtruncate that has the necessary locking
semantics.

The result should be that the following inode attribute updates are
protected by inode->i_lock
	nfsi->cache_validity
	nfsi->read_cache_jiffies
	nfsi->attrtimeo
	nfsi->attrtimeo_timestamp
	nfsi->change_attr
	nfsi->last_updated
	nfsi->cache_change_attribute
	nfsi->access_cache
	nfsi->access_cache_entry_lru
	nfsi->access_cache_inode_lru
	nfsi->acl_access
	nfsi->acl_default
	nfsi->nfs_page_tree
	nfsi->ncommit
	nfsi->npages
	nfsi->open_files
	nfsi->silly_list
	nfsi->acl
	nfsi->open_states
	inode->i_size
	inode->i_atime
	inode->i_mtime
	inode->i_ctime
	inode->i_nlink
	inode->i_uid
	inode->i_gid

The following is protected by dir->i_mutex
	nfsi->cookieverf

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 61 insertions, 6 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 2c23d067e2a6..3adabd154779 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -389,6 +389,62 @@ nfs_setattr(struct dentry *dentry, struct iattr *attr)
 }
 
 /**
+ * nfs_vmtruncate - unmap mappings "freed" by truncate() syscall
+ * @inode: inode of the file used
+ * @offset: file offset to start truncating
+ *
+ * This is a copy of the common vmtruncate, but with the locking
+ * corrected to take into account the fact that NFS requires
+ * inode->i_size to be updated under the inode->i_lock.
+ */
+static int nfs_vmtruncate(struct inode * inode, loff_t offset)
+{
+        if (i_size_read(inode) < offset) {
+                unsigned long limit;
+
+                limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
+                if (limit != RLIM_INFINITY && offset > limit)
+                        goto out_sig;
+                if (offset > inode->i_sb->s_maxbytes)
+                        goto out_big;
+                spin_lock(&inode->i_lock);
+                i_size_write(inode, offset);
+                spin_unlock(&inode->i_lock);
+        } else {
+                struct address_space *mapping = inode->i_mapping;
+
+                /*
+                 * truncation of in-use swapfiles is disallowed - it would
+                 * cause subsequent swapout to scribble on the now-freed
+                 * blocks.
+                 */
+                if (IS_SWAPFILE(inode))
+                        return -ETXTBSY;
+                spin_lock(&inode->i_lock);
+                i_size_write(inode, offset);
+                spin_unlock(&inode->i_lock);
+
+                /*
+                 * unmap_mapping_range is called twice, first simply for
+                 * efficiency so that truncate_inode_pages does fewer
+                 * single-page unmaps.  However after this first call, and
+                 * before truncate_inode_pages finishes, it is possible for
+                 * private pages to be COWed, which remain after
+                 * truncate_inode_pages finishes, hence the second
+                 * unmap_mapping_range call must be made for correctness.
+                 */
+                unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
+                truncate_inode_pages(mapping, offset);
+                unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
+        }
+        return 0;
+out_sig:
+        send_sig(SIGXFSZ, current, 0);
+out_big:
+        return -EFBIG;
+}
+
+/**
  * nfs_setattr_update_inode - Update inode metadata after a setattr call.
  * @inode: pointer to struct inode
  * @attr: pointer to struct iattr
@@ -414,8 +470,7 @@ void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr)
         }
         if ((attr->ia_valid & ATTR_SIZE) != 0) {
                 nfs_inc_stats(inode, NFSIOS_SETATTRTRUNC);
-                inode->i_size = attr->ia_size;
-                vmtruncate(inode, attr->ia_size);
+                nfs_vmtruncate(inode, attr->ia_size);
         }
 }
 
@@ -829,9 +884,9 @@ static void nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr *fattr)
                         if (S_ISDIR(inode->i_mode))
                                 nfsi->cache_validity |= NFS_INO_INVALID_DATA;
                 }
-                if (inode->i_size == nfs_size_to_loff_t(fattr->pre_size) &&
+                if (i_size_read(inode) == nfs_size_to_loff_t(fattr->pre_size) &&
                     nfsi->npages == 0)
-                        inode->i_size = nfs_size_to_loff_t(fattr->size);
+                        i_size_write(inode, nfs_size_to_loff_t(fattr->size));
         }
 }
 
@@ -972,7 +1027,7 @@ int nfs_post_op_update_inode_force_wcc(struct inode *inode, struct nfs_fattr *fa
                         (fattr->valid & NFS_ATTR_WCC) == 0) {
                 memcpy(&fattr->pre_ctime, &inode->i_ctime, sizeof(fattr->pre_ctime));
                 memcpy(&fattr->pre_mtime, &inode->i_mtime, sizeof(fattr->pre_mtime));
-                fattr->pre_size = inode->i_size;
+                fattr->pre_size = i_size_read(inode);
                 fattr->valid |= NFS_ATTR_WCC;
         }
         return nfs_post_op_update_inode(inode, fattr);
@@ -1057,7 +1112,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
                 /* Do we perhaps have any outstanding writes, or has
                  * the file grown beyond our last write? */
                 if (nfsi->npages == 0 || new_isize > cur_isize) {
-                        inode->i_size = new_isize;
+                        i_size_write(inode, new_isize);
                         invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;
                 }
                 dprintk("NFS: isize change on server for file %s/%ld\n",