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![David Howells](/assets/img/avatar_default.png)
commit2105c2820d
upstream. AFS directories are retained locally as a structured file, with lookup being effected by a local search of the file contents. When a modification (such as mkdir) happens, the dir file content is modified locally rather than redownloading the directory. The directory contents are accessed in a number of ways, with a number of different locks schemes: (1) Download of contents - dvnode->validate_lock/write in afs_read_dir(). (2) Lookup and readdir - dvnode->validate_lock/read in afs_dir_iterate(), downgrading from (1) if necessary. (3) d_revalidate of child dentry - dvnode->validate_lock/read in afs_do_lookup_one() downgrading from (1) if necessary. (4) Edit of dir after modification - page locks on individual dir pages. Unfortunately, because (4) uses different locking scheme to (1) - (3), nothing protects against the page being scanned whilst the edit is underway. Even download is not safe as it doesn't lock the pages - relying instead on the validate_lock to serialise as a whole (the theory being that directory contents are treated as a block and always downloaded as a block). Fix this by write-locking dvnode->validate_lock around the edits. Care must be taken in the rename case as there may be two different dirs - but they need not be locked at the same time. In any case, once the lock is taken, the directory version must be rechecked, and the edit skipped if a later version has been downloaded by revalidation (there can't have been any local changes because the VFS holds the inode lock, but there can have been remote changes). Fixes:63a4681ff3
("afs: Locally edit directory data for mkdir/create/unlink/...") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
253 lines
6.6 KiB
C
253 lines
6.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* AFS silly rename handling
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*
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* Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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* - Derived from NFS's sillyrename.
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*/
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/namei.h>
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#include <linux/fsnotify.h>
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#include "internal.h"
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/*
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* Actually perform the silly rename step.
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*/
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static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
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struct dentry *old, struct dentry *new,
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struct key *key)
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{
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struct afs_fs_cursor fc;
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struct afs_status_cb *scb;
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afs_dataversion_t dir_data_version;
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int ret = -ERESTARTSYS;
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_enter("%pd,%pd", old, new);
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scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
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if (!scb)
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return -ENOMEM;
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trace_afs_silly_rename(vnode, false);
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if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {
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dir_data_version = dvnode->status.data_version + 1;
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while (afs_select_fileserver(&fc)) {
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fc.cb_break = afs_calc_vnode_cb_break(dvnode);
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afs_fs_rename(&fc, old->d_name.name,
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dvnode, new->d_name.name,
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scb, scb);
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}
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afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
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&dir_data_version, scb);
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ret = afs_end_vnode_operation(&fc);
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}
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if (ret == 0) {
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spin_lock(&old->d_lock);
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old->d_flags |= DCACHE_NFSFS_RENAMED;
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spin_unlock(&old->d_lock);
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if (dvnode->silly_key != key) {
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key_put(dvnode->silly_key);
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dvnode->silly_key = key_get(key);
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}
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down_write(&dvnode->validate_lock);
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if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
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dvnode->status.data_version == dir_data_version) {
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afs_edit_dir_remove(dvnode, &old->d_name,
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afs_edit_dir_for_silly_0);
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afs_edit_dir_add(dvnode, &new->d_name,
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&vnode->fid, afs_edit_dir_for_silly_1);
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}
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up_write(&dvnode->validate_lock);
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}
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kfree(scb);
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_leave(" = %d", ret);
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return ret;
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}
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/**
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* afs_sillyrename - Perform a silly-rename of a dentry
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*
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* AFS is stateless and the server doesn't know when the client is holding a
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* file open. To prevent application problems when a file is unlinked while
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* it's still open, the client performs a "silly-rename". That is, it renames
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* the file to a hidden file in the same directory, and only performs the
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* unlink once the last reference to it is put.
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*
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* The final cleanup is done during dentry_iput.
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*/
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int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
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struct dentry *dentry, struct key *key)
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{
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static unsigned int sillycounter;
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struct dentry *sdentry = NULL;
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unsigned char silly[16];
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int ret = -EBUSY;
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_enter("");
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/* We don't allow a dentry to be silly-renamed twice. */
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if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
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return -EBUSY;
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sdentry = NULL;
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do {
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int slen;
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dput(sdentry);
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sillycounter++;
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/* Create a silly name. Note that the ".__afs" prefix is
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* understood by the salvager and must not be changed.
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*/
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slen = scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
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sdentry = lookup_one_len(silly, dentry->d_parent, slen);
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/* N.B. Better to return EBUSY here ... it could be dangerous
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* to delete the file while it's in use.
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*/
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if (IS_ERR(sdentry))
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goto out;
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} while (!d_is_negative(sdentry));
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ihold(&vnode->vfs_inode);
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ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
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switch (ret) {
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case 0:
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/* The rename succeeded. */
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d_move(dentry, sdentry);
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break;
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case -ERESTARTSYS:
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/* The result of the rename is unknown. Play it safe by forcing
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* a new lookup.
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*/
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d_drop(dentry);
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d_drop(sdentry);
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}
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iput(&vnode->vfs_inode);
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dput(sdentry);
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out:
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_leave(" = %d", ret);
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return ret;
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}
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/*
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* Tell the server to remove a sillyrename file.
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*/
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static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode,
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struct dentry *dentry, struct key *key)
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{
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struct afs_fs_cursor fc;
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struct afs_status_cb *scb;
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int ret = -ERESTARTSYS;
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_enter("");
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scb = kcalloc(2, sizeof(struct afs_status_cb), GFP_KERNEL);
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if (!scb)
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return -ENOMEM;
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trace_afs_silly_rename(vnode, true);
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if (afs_begin_vnode_operation(&fc, dvnode, key, false)) {
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afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;
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while (afs_select_fileserver(&fc)) {
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fc.cb_break = afs_calc_vnode_cb_break(dvnode);
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if (test_bit(AFS_SERVER_FL_IS_YFS, &fc.cbi->server->flags) &&
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!test_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags)) {
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yfs_fs_remove_file2(&fc, vnode, dentry->d_name.name,
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&scb[0], &scb[1]);
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if (fc.ac.error != -ECONNABORTED ||
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fc.ac.abort_code != RXGEN_OPCODE)
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continue;
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set_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags);
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}
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afs_fs_remove(&fc, vnode, dentry->d_name.name, false, &scb[0]);
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}
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afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
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&dir_data_version, &scb[0]);
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ret = afs_end_vnode_operation(&fc);
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if (ret == 0) {
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drop_nlink(&vnode->vfs_inode);
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if (vnode->vfs_inode.i_nlink == 0) {
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set_bit(AFS_VNODE_DELETED, &vnode->flags);
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clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
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}
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}
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if (ret == 0) {
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down_write(&dvnode->validate_lock);
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if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
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dvnode->status.data_version == dir_data_version)
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afs_edit_dir_remove(dvnode, &dentry->d_name,
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afs_edit_dir_for_unlink);
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up_write(&dvnode->validate_lock);
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}
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}
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kfree(scb);
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_leave(" = %d", ret);
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return ret;
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}
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/*
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* Remove sillyrename file on iput.
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*/
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int afs_silly_iput(struct dentry *dentry, struct inode *inode)
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{
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struct afs_vnode *dvnode = AFS_FS_I(d_inode(dentry->d_parent));
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struct afs_vnode *vnode = AFS_FS_I(inode);
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struct dentry *alias;
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int ret;
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DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
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_enter("%p{%pd},%llx", dentry, dentry, vnode->fid.vnode);
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down_read(&dvnode->rmdir_lock);
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alias = d_alloc_parallel(dentry->d_parent, &dentry->d_name, &wq);
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if (IS_ERR(alias)) {
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up_read(&dvnode->rmdir_lock);
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return 0;
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}
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if (!d_in_lookup(alias)) {
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/* We raced with lookup... See if we need to transfer the
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* sillyrename information to the aliased dentry.
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*/
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ret = 0;
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spin_lock(&alias->d_lock);
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if (d_really_is_positive(alias) &&
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!(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
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alias->d_flags |= DCACHE_NFSFS_RENAMED;
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ret = 1;
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}
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spin_unlock(&alias->d_lock);
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up_read(&dvnode->rmdir_lock);
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dput(alias);
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return ret;
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}
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/* Stop lock-release from complaining. */
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spin_lock(&vnode->lock);
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vnode->lock_state = AFS_VNODE_LOCK_DELETED;
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trace_afs_flock_ev(vnode, NULL, afs_flock_silly_delete, 0);
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spin_unlock(&vnode->lock);
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afs_do_silly_unlink(dvnode, vnode, dentry, dvnode->silly_key);
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up_read(&dvnode->rmdir_lock);
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d_lookup_done(alias);
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dput(alias);
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return 1;
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}
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