From 451d0f599934fd97faf54a5d7954b518e66192cb Mon Sep 17 00:00:00 2001 From: John Muir Date: Tue, 6 Dec 2011 21:50:06 +0100 Subject: [PATCH] FUSE: Notifying the kernel of deletion. Allows a FUSE file-system to tell the kernel when a file or directory is deleted. If the specified dentry has the specified inode number, the kernel will unhash it. The current 'fuse_notify_inval_entry' does not cause the kernel to clean up directories that are in use properly, and as a result the users of those directories see incorrect semantics from the file-system. The error condition seen when 'fuse_notify_inval_entry' is used to notify of a deleted directory is avoided when 'fuse_notify_delete' is used instead. The following scenario demonstrates the difference: 1. User A chdirs into 'testdir' and starts reading 'testfile'. 2. User B rm -rf 'testdir'. 3. User B creates 'testdir'. 4. User C chdirs into 'testdir'. If you run the above within the same machine on any file-system (including fuse file-systems), there is no problem: user C is able to chdir into the new testdir. The old testdir is removed from the dentry tree, but still open by user A. If operations 2 and 3 are performed via the network such that the fuse file-system uses one of the notify functions to tell the kernel that the nodes are gone, then the following error occurs for user C while user A holds the original directory open: muirj@empacher:~> ls /test/testdir ls: cannot access /test/testdir: No such file or directory The issue here is that the kernel still has a dentry for testdir, and so it is requesting the attributes for the old directory, while the file-system is responding that the directory no longer exists. If on the other hand, if the file-system can notify the kernel that the directory is deleted using the new 'fuse_notify_delete' function, then the above ls will find the new directory as expected. Signed-off-by: John Muir Signed-off-by: Miklos Szeredi --- fs/fuse/dev.c | 57 +++++++++++++++++++++++++++++++++++++++++++- fs/fuse/dir.c | 32 +++++++++++++++++++++++-- fs/fuse/fuse_i.h | 8 ++++++- include/linux/fuse.h | 9 +++++++ 4 files changed, 102 insertions(+), 4 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 2aaf3eaaf13d..5f3368ab0fa9 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1378,7 +1378,59 @@ static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size, down_read(&fc->killsb); err = -ENOENT; if (fc->sb) - err = fuse_reverse_inval_entry(fc->sb, outarg.parent, &name); + err = fuse_reverse_inval_entry(fc->sb, outarg.parent, 0, &name); + up_read(&fc->killsb); + kfree(buf); + return err; + +err: + kfree(buf); + fuse_copy_finish(cs); + return err; +} + +static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size, + struct fuse_copy_state *cs) +{ + struct fuse_notify_delete_out outarg; + int err = -ENOMEM; + char *buf; + struct qstr name; + + buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL); + if (!buf) + goto err; + + err = -EINVAL; + if (size < sizeof(outarg)) + goto err; + + err = fuse_copy_one(cs, &outarg, sizeof(outarg)); + if (err) + goto err; + + err = -ENAMETOOLONG; + if (outarg.namelen > FUSE_NAME_MAX) + goto err; + + err = -EINVAL; + if (size != sizeof(outarg) + outarg.namelen + 1) + goto err; + + name.name = buf; + name.len = outarg.namelen; + err = fuse_copy_one(cs, buf, outarg.namelen + 1); + if (err) + goto err; + fuse_copy_finish(cs); + buf[outarg.namelen] = 0; + name.hash = full_name_hash(name.name, name.len); + + down_read(&fc->killsb); + err = -ENOENT; + if (fc->sb) + err = fuse_reverse_inval_entry(fc->sb, outarg.parent, + outarg.child, &name); up_read(&fc->killsb); kfree(buf); return err; @@ -1597,6 +1649,9 @@ static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code, case FUSE_NOTIFY_RETRIEVE: return fuse_notify_retrieve(fc, size, cs); + case FUSE_NOTIFY_DELETE: + return fuse_notify_delete(fc, size, cs); + default: fuse_copy_finish(cs); return -EINVAL; diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 344577933f62..bef8c3011d31 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -868,7 +868,7 @@ int fuse_update_attributes(struct inode *inode, struct kstat *stat, } int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid, - struct qstr *name) + u64 child_nodeid, struct qstr *name) { int err = -ENOTDIR; struct inode *parent; @@ -895,8 +895,36 @@ int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid, fuse_invalidate_attr(parent); fuse_invalidate_entry(entry); + + if (child_nodeid != 0 && entry->d_inode) { + mutex_lock(&entry->d_inode->i_mutex); + if (get_node_id(entry->d_inode) != child_nodeid) { + err = -ENOENT; + goto badentry; + } + if (d_mountpoint(entry)) { + err = -EBUSY; + goto badentry; + } + if (S_ISDIR(entry->d_inode->i_mode)) { + shrink_dcache_parent(entry); + if (!simple_empty(entry)) { + err = -ENOTEMPTY; + goto badentry; + } + entry->d_inode->i_flags |= S_DEAD; + } + dont_mount(entry); + clear_nlink(entry->d_inode); + err = 0; + badentry: + mutex_unlock(&entry->d_inode->i_mutex); + if (!err) + d_delete(entry); + } else { + err = 0; + } dput(entry); - err = 0; unlock: mutex_unlock(&parent->i_mutex); diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 09337bcc2554..a571584a091a 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -755,9 +755,15 @@ int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid, /** * File-system tells the kernel to invalidate parent attributes and * the dentry matching parent/name. + * + * If the child_nodeid is non-zero and: + * - matches the inode number for the dentry matching parent/name, + * - is not a mount point + * - is a file or oan empty directory + * then the dentry is unhashed (d_delete()). */ int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid, - struct qstr *name); + u64 child_nodeid, struct qstr *name); int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file, bool isdir); diff --git a/include/linux/fuse.h b/include/linux/fuse.h index 446c89718b9c..8ba2c9460b28 100644 --- a/include/linux/fuse.h +++ b/include/linux/fuse.h @@ -53,6 +53,7 @@ * * 7.18 * - add FUSE_IOCTL_DIR flag + * - add FUSE_NOTIFY_DELETE */ #ifndef _LINUX_FUSE_H @@ -288,6 +289,7 @@ enum fuse_notify_code { FUSE_NOTIFY_INVAL_ENTRY = 3, FUSE_NOTIFY_STORE = 4, FUSE_NOTIFY_RETRIEVE = 5, + FUSE_NOTIFY_DELETE = 6, FUSE_NOTIFY_CODE_MAX, }; @@ -611,6 +613,13 @@ struct fuse_notify_inval_entry_out { __u32 padding; }; +struct fuse_notify_delete_out { + __u64 parent; + __u64 child; + __u32 namelen; + __u32 padding; +}; + struct fuse_notify_store_out { __u64 nodeid; __u64 offset; -- 2.34.1