fuse: support writable mmap

[linux-2.6-omap-h63xx.git] / fs / fuse / dir.c

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index c4807b3fc8a360776bda6f976baebd26b5c9ae92..48b9971ecd97d067d6adc8cee0a6e4e281e5a093 100644 (file)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1106,6 +1106,50 @@ static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg)
        }
 }
 
+/*
+ * Prevent concurrent writepages on inode
+ *
+ * This is done by adding a negative bias to the inode write counter
+ * and waiting for all pending writes to finish.
+ */
+void fuse_set_nowrite(struct inode *inode)
+{
+       struct fuse_conn *fc = get_fuse_conn(inode);
+       struct fuse_inode *fi = get_fuse_inode(inode);
+
+       BUG_ON(!mutex_is_locked(&inode->i_mutex));
+
+       spin_lock(&fc->lock);
+       BUG_ON(fi->writectr < 0);
+       fi->writectr += FUSE_NOWRITE;
+       spin_unlock(&fc->lock);
+       wait_event(fi->page_waitq, fi->writectr == FUSE_NOWRITE);
+}
+
+/*
+ * Allow writepages on inode
+ *
+ * Remove the bias from the writecounter and send any queued
+ * writepages.
+ */
+static void __fuse_release_nowrite(struct inode *inode)
+{
+       struct fuse_inode *fi = get_fuse_inode(inode);
+
+       BUG_ON(fi->writectr != FUSE_NOWRITE);
+       fi->writectr = 0;
+       fuse_flush_writepages(inode);
+}
+
+void fuse_release_nowrite(struct inode *inode)
+{
+       struct fuse_conn *fc = get_fuse_conn(inode);
+
+       spin_lock(&fc->lock);
+       __fuse_release_nowrite(inode);
+       spin_unlock(&fc->lock);
+}
+
 /*
  * Set attributes, and at the same time refresh them.
  *
@@ -1122,6 +1166,8 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
        struct fuse_req *req;
        struct fuse_setattr_in inarg;
        struct fuse_attr_out outarg;
+       bool is_truncate = false;
+       loff_t oldsize;
        int err;
 
        if (!fuse_allow_task(fc, current))
@@ -1145,12 +1191,16 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
                        send_sig(SIGXFSZ, current, 0);
                        return -EFBIG;
                }
+               is_truncate = true;
        }
 
        req = fuse_get_req(fc);
        if (IS_ERR(req))
                return PTR_ERR(req);
 
+       if (is_truncate)
+               fuse_set_nowrite(inode);
+
        memset(&inarg, 0, sizeof(inarg));
        memset(&outarg, 0, sizeof(outarg));
        iattr_to_fattr(attr, &inarg);
@@ -1181,16 +1231,44 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
        if (err) {
                if (err == -EINTR)
                        fuse_invalidate_attr(inode);
-               return err;
+               goto error;
        }
 
        if ((inode->i_mode ^ outarg.attr.mode) & S_IFMT) {
                make_bad_inode(inode);
-               return -EIO;
+               err = -EIO;
+               goto error;
+       }
+
+       spin_lock(&fc->lock);
+       fuse_change_attributes_common(inode, &outarg.attr,
+                                     attr_timeout(&outarg));
+       oldsize = inode->i_size;
+       i_size_write(inode, outarg.attr.size);
+
+       if (is_truncate) {
+               /* NOTE: this may release/reacquire fc->lock */
+               __fuse_release_nowrite(inode);
+       }
+       spin_unlock(&fc->lock);
+
+       /*
+        * Only call invalidate_inode_pages2() after removing
+        * FUSE_NOWRITE, otherwise fuse_launder_page() would deadlock.
+        */
+       if (S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
+               if (outarg.attr.size < oldsize)
+                       fuse_truncate(inode->i_mapping, outarg.attr.size);
+               invalidate_inode_pages2(inode->i_mapping);
        }
 
-       fuse_change_attributes(inode, &outarg.attr, attr_timeout(&outarg), 0);
        return 0;
+
+error:
+       if (is_truncate)
+               fuse_release_nowrite(inode);
+
+       return err;
 }
 
 static int fuse_setattr(struct dentry *entry, struct iattr *attr)