linux/fs/afs/dir_silly.c
David Howells a58823ac45 afs: Fix application of status and callback to be under same lock
When applying the status and callback in the response of an operation,
apply them in the same critical section so that there's no race between
checking the callback state and checking status-dependent state (such as
the data version).

Fix this by:

 (1) Allocating a joint {status,callback} record (afs_status_cb) before
     calling the RPC function for each vnode for which the RPC reply
     contains a status or a status plus a callback.  A flag is set in the
     record to indicate if a callback was actually received.

 (2) These records are passed into the RPC functions to be filled in.  The
     afs_decode_status() and yfs_decode_status() functions are removed and
     the cb_lock is no longer taken.

 (3) xdr_decode_AFSFetchStatus() and xdr_decode_YFSFetchStatus() no longer
     update the vnode.

 (4) xdr_decode_AFSCallBack() and xdr_decode_YFSCallBack() no longer update
     the vnode.

 (5) vnodes, expected data-version numbers and callback break counters
     (cb_break) no longer need to be passed to the reply delivery
     functions.

     Note that, for the moment, the file locking functions still need
     access to both the call and the vnode at the same time.

 (6) afs_vnode_commit_status() is now given the cb_break value and the
     expected data_version and the task of applying the status and the
     callback to the vnode are now done here.

     This is done under a single taking of vnode->cb_lock.

 (7) afs_pages_written_back() is now called by afs_store_data() rather than
     by the reply delivery function.

     afs_pages_written_back() has been moved to before the call point and
     is now given the first and last page numbers rather than a pointer to
     the call.

 (8) The indicator from YFS.RemoveFile2 as to whether the target file
     actually got removed (status.abort_code == VNOVNODE) rather than
     merely dropping a link is now checked in afs_unlink rather than in
     xdr_decode_YFSFetchStatus().

Supplementary fixes:

 (*) afs_cache_permit() now gets the caller_access mask from the
     afs_status_cb object rather than picking it out of the vnode's status
     record.  afs_fetch_status() returns caller_access through its argument
     list for this purpose also.

 (*) afs_inode_init_from_status() now uses a write lock on cb_lock rather
     than a read lock and now sets the callback inside the same critical
     section.

Fixes: c435ee3455 ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>
2019-05-16 16:25:21 +01:00

255 lines
6.7 KiB
C

/* AFS silly rename handling
*
* Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
* - Derived from NFS's sillyrename.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/fsnotify.h>
#include "internal.h"
/*
* Actually perform the silly rename step.
*/
static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
struct dentry *old, struct dentry *new,
struct key *key)
{
struct afs_fs_cursor fc;
struct afs_status_cb *scb;
int ret = -ERESTARTSYS;
_enter("%pd,%pd", old, new);
scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
if (!scb)
return -ENOMEM;
trace_afs_silly_rename(vnode, false);
if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {
afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;
while (afs_select_fileserver(&fc)) {
fc.cb_break = afs_calc_vnode_cb_break(dvnode);
afs_fs_rename(&fc, old->d_name.name,
dvnode, new->d_name.name,
scb, scb);
}
afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
&dir_data_version, scb);
ret = afs_end_vnode_operation(&fc);
}
if (ret == 0) {
spin_lock(&old->d_lock);
old->d_flags |= DCACHE_NFSFS_RENAMED;
spin_unlock(&old->d_lock);
if (dvnode->silly_key != key) {
key_put(dvnode->silly_key);
dvnode->silly_key = key_get(key);
}
if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
afs_edit_dir_remove(dvnode, &old->d_name,
afs_edit_dir_for_silly_0);
if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
afs_edit_dir_add(dvnode, &new->d_name,
&vnode->fid, afs_edit_dir_for_silly_1);
/* vfs_unlink and the like do not issue this when a file is
* sillyrenamed, so do it here.
*/
fsnotify_nameremove(old, 0);
}
kfree(scb);
_leave(" = %d", ret);
return ret;
}
/**
* afs_sillyrename - Perform a silly-rename of a dentry
*
* AFS is stateless and the server doesn't know when the client is holding a
* file open. To prevent application problems when a file is unlinked while
* it's still open, the client performs a "silly-rename". That is, it renames
* the file to a hidden file in the same directory, and only performs the
* unlink once the last reference to it is put.
*
* The final cleanup is done during dentry_iput.
*/
int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
struct dentry *dentry, struct key *key)
{
static unsigned int sillycounter;
struct dentry *sdentry = NULL;
unsigned char silly[16];
int ret = -EBUSY;
_enter("");
/* We don't allow a dentry to be silly-renamed twice. */
if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
return -EBUSY;
sdentry = NULL;
do {
int slen;
dput(sdentry);
sillycounter++;
/* Create a silly name. Note that the ".__afs" prefix is
* understood by the salvager and must not be changed.
*/
slen = scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
sdentry = lookup_one_len(silly, dentry->d_parent, slen);
/* N.B. Better to return EBUSY here ... it could be dangerous
* to delete the file while it's in use.
*/
if (IS_ERR(sdentry))
goto out;
} while (!d_is_negative(sdentry));
ihold(&vnode->vfs_inode);
ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
switch (ret) {
case 0:
/* The rename succeeded. */
d_move(dentry, sdentry);
break;
case -ERESTARTSYS:
/* The result of the rename is unknown. Play it safe by forcing
* a new lookup.
*/
d_drop(dentry);
d_drop(sdentry);
}
iput(&vnode->vfs_inode);
dput(sdentry);
out:
_leave(" = %d", ret);
return ret;
}
/*
* Tell the server to remove a sillyrename file.
*/
static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode,
struct dentry *dentry, struct key *key)
{
struct afs_fs_cursor fc;
struct afs_status_cb *scb;
int ret = -ERESTARTSYS;
_enter("");
scb = kcalloc(2, sizeof(struct afs_status_cb), GFP_KERNEL);
if (!scb)
return -ENOMEM;
trace_afs_silly_rename(vnode, true);
if (afs_begin_vnode_operation(&fc, dvnode, key, false)) {
afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;
while (afs_select_fileserver(&fc)) {
fc.cb_break = afs_calc_vnode_cb_break(dvnode);
if (test_bit(AFS_SERVER_FL_IS_YFS, &fc.cbi->server->flags) &&
!test_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags)) {
yfs_fs_remove_file2(&fc, vnode, dentry->d_name.name,
&scb[0], &scb[1]);
if (fc.ac.error != -ECONNABORTED ||
fc.ac.abort_code != RXGEN_OPCODE)
continue;
set_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags);
}
afs_fs_remove(&fc, vnode, dentry->d_name.name, false, &scb[0]);
}
afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
&dir_data_version, &scb[0]);
ret = afs_end_vnode_operation(&fc);
if (ret == 0) {
drop_nlink(&vnode->vfs_inode);
if (vnode->vfs_inode.i_nlink == 0) {
set_bit(AFS_VNODE_DELETED, &vnode->flags);
clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
}
}
if (ret == 0 &&
test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
afs_edit_dir_remove(dvnode, &dentry->d_name,
afs_edit_dir_for_unlink);
}
kfree(scb);
_leave(" = %d", ret);
return ret;
}
/*
* Remove sillyrename file on iput.
*/
int afs_silly_iput(struct dentry *dentry, struct inode *inode)
{
struct afs_vnode *dvnode = AFS_FS_I(d_inode(dentry->d_parent));
struct afs_vnode *vnode = AFS_FS_I(inode);
struct dentry *alias;
int ret;
DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
_enter("%p{%pd},%llx", dentry, dentry, vnode->fid.vnode);
down_read(&dvnode->rmdir_lock);
alias = d_alloc_parallel(dentry->d_parent, &dentry->d_name, &wq);
if (IS_ERR(alias)) {
up_read(&dvnode->rmdir_lock);
return 0;
}
if (!d_in_lookup(alias)) {
/* We raced with lookup... See if we need to transfer the
* sillyrename information to the aliased dentry.
*/
ret = 0;
spin_lock(&alias->d_lock);
if (d_really_is_positive(alias) &&
!(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
alias->d_flags |= DCACHE_NFSFS_RENAMED;
ret = 1;
}
spin_unlock(&alias->d_lock);
up_read(&dvnode->rmdir_lock);
dput(alias);
return ret;
}
/* Stop lock-release from complaining. */
spin_lock(&vnode->lock);
vnode->lock_state = AFS_VNODE_LOCK_DELETED;
trace_afs_flock_ev(vnode, NULL, afs_flock_silly_delete, 0);
spin_unlock(&vnode->lock);
afs_do_silly_unlink(dvnode, vnode, dentry, dvnode->silly_key);
up_read(&dvnode->rmdir_lock);
d_lookup_done(alias);
dput(alias);
return 1;
}