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![David Howells](/assets/img/avatar_default.png)
The current code assumes that volumes and servers are per-cell and are never shared, but this is not enforced, and, indeed, public cells do exist that are aliases of each other. Further, an organisation can, say, set up a public cell and a private cell with overlapping, but not identical, sets of servers. The difference is purely in the database attached to the VL servers. The current code will malfunction if it sees a server in two cells as it assumes global address -> server record mappings and that each server is in just one cell. Further, each server may have multiple addresses - and may have addresses of different families (IPv4 and IPv6, say). To this end, the following structural changes are made: (1) Server record management is overhauled: (a) Server records are made independent of cell. The namespace keeps track of them, volume records have lists of them and each vnode has a server on which its callback interest currently resides. (b) The cell record no longer keeps a list of servers known to be in that cell. (c) The server records are now kept in a flat list because there's no single address to sort on. (d) Server records are now keyed by their UUID within the namespace. (e) The addresses for a server are obtained with the VL.GetAddrsU rather than with VL.GetEntryByName, using the server's UUID as a parameter. (f) Cached server records are garbage collected after a period of non-use and are counted out of existence before purging is allowed to complete. This protects the work functions against rmmod. (g) The servers list is now in /proc/fs/afs/servers. (2) Volume record management is overhauled: (a) An RCU-replaceable server list is introduced. This tracks both servers and their coresponding callback interests. (b) The superblock is now keyed on cell record and numeric volume ID. (c) The volume record is now tied to the superblock which mounts it, and is activated when mounted and deactivated when unmounted. This makes it easier to handle the cache cookie without causing a double-use in fscache. (d) The volume record is loaded from the VLDB using VL.GetEntryByNameU to get the server UUID list. (e) The volume name is updated if it is seen to have changed when the volume is updated (the update is keyed on the volume ID). (3) The vlocation record is got rid of and VLDB records are no longer cached. Sufficient information is stored in the volume record, though an update to a volume record is now no longer shared between related volumes (volumes come in bundles of three: R/W, R/O and backup). and the following procedural changes are made: (1) The fileserver cursor introduced previously is now fleshed out and used to iterate over fileservers and their addresses. (2) Volume status is checked during iteration, and the server list is replaced if a change is detected. (3) Server status is checked during iteration, and the address list is replaced if a change is detected. (4) The abort code is saved into the address list cursor and -ECONNABORTED returned in afs_make_call() if a remote abort happened rather than translating the abort into an error message. This allows actions to be taken depending on the abort code more easily. (a) If a VMOVED abort is seen then this is handled by rechecking the volume and restarting the iteration. (b) If a VBUSY, VRESTARTING or VSALVAGING abort is seen then this is handled by sleeping for a short period and retrying and/or trying other servers that might serve that volume. A message is also displayed once until the condition has cleared. (c) If a VOFFLINE abort is seen, then this is handled as VBUSY for the moment. (d) If a VNOVOL abort is seen, the volume is rechecked in the VLDB to see if it has been deleted; if not, the fileserver is probably indicating that the volume couldn't be attached and needs salvaging. (e) If statfs() sees one of these aborts, it does not sleep, but rather returns an error, so as not to block the umount program. (5) The fileserver iteration functions in vnode.c are now merged into their callers and more heavily macroised around the cursor. vnode.c is removed. (6) Operations on a particular vnode are serialised on that vnode because the server will lock that vnode whilst it operates on it, so a second op sent will just have to wait. (7) Fileservers are probed with FS.GetCapabilities before being used. This is where service upgrade will be done. (8) A callback interest on a fileserver is set up before an FS operation is performed and passed through to afs_make_call() so that it can be set on the vnode if the operation returns a callback. The callback interest is passed through to afs_iget() also so that it can be set there too. In general, record updating is done on an as-needed basis when we try to access servers, volumes or vnodes rather than offloading it to work items and special threads. Notes: (1) Pre AFS-3.4 servers are no longer supported, though this can be added back if necessary (AFS-3.4 was released in 1998). (2) VBUSY is retried forever for the moment at intervals of 1s. (3) /proc/fs/afs/<cell>/servers no longer exists. Signed-off-by: David Howells <dhowells@redhat.com>
121 lines
3 KiB
C
121 lines
3 KiB
C
/* Extended attribute handling for AFS. We use xattrs to get and set metadata
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* instead of providing pioctl().
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*
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* Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/xattr.h>
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#include "internal.h"
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static const char afs_xattr_list[] =
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"afs.cell\0"
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"afs.fid\0"
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"afs.volume";
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/*
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* Retrieve a list of the supported xattrs.
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*/
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ssize_t afs_listxattr(struct dentry *dentry, char *buffer, size_t size)
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{
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if (size == 0)
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return sizeof(afs_xattr_list);
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if (size < sizeof(afs_xattr_list))
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return -ERANGE;
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memcpy(buffer, afs_xattr_list, sizeof(afs_xattr_list));
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return sizeof(afs_xattr_list);
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}
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/*
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* Get the name of the cell on which a file resides.
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*/
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static int afs_xattr_get_cell(const struct xattr_handler *handler,
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struct dentry *dentry,
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struct inode *inode, const char *name,
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void *buffer, size_t size)
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{
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struct afs_vnode *vnode = AFS_FS_I(inode);
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struct afs_cell *cell = vnode->volume->cell;
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size_t namelen;
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namelen = cell->name_len;
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if (size == 0)
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return namelen;
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if (namelen > size)
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return -ERANGE;
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memcpy(buffer, cell->name, size);
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return namelen;
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}
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static const struct xattr_handler afs_xattr_afs_cell_handler = {
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.name = "afs.cell",
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.get = afs_xattr_get_cell,
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};
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/*
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* Get the volume ID, vnode ID and vnode uniquifier of a file as a sequence of
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* hex numbers separated by colons.
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*/
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static int afs_xattr_get_fid(const struct xattr_handler *handler,
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struct dentry *dentry,
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struct inode *inode, const char *name,
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void *buffer, size_t size)
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{
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struct afs_vnode *vnode = AFS_FS_I(inode);
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char text[8 + 1 + 8 + 1 + 8 + 1];
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size_t len;
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len = sprintf(text, "%x:%x:%x",
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vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
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if (size == 0)
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return len;
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if (len > size)
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return -ERANGE;
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memcpy(buffer, text, len);
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return len;
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}
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static const struct xattr_handler afs_xattr_afs_fid_handler = {
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.name = "afs.fid",
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.get = afs_xattr_get_fid,
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};
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/*
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* Get the name of the volume on which a file resides.
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*/
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static int afs_xattr_get_volume(const struct xattr_handler *handler,
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struct dentry *dentry,
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struct inode *inode, const char *name,
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void *buffer, size_t size)
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{
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struct afs_vnode *vnode = AFS_FS_I(inode);
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const char *volname = vnode->volume->name;
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size_t namelen;
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namelen = strlen(volname);
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if (size == 0)
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return namelen;
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if (namelen > size)
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return -ERANGE;
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memcpy(buffer, volname, size);
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return namelen;
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}
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static const struct xattr_handler afs_xattr_afs_volume_handler = {
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.name = "afs.volume",
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.get = afs_xattr_get_volume,
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};
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const struct xattr_handler *afs_xattr_handlers[] = {
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&afs_xattr_afs_cell_handler,
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&afs_xattr_afs_fid_handler,
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&afs_xattr_afs_volume_handler,
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NULL
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};
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