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Re-factor the .zfs/snapshot auto-mouting code to take in to account changes made to the upstream kernels. And to lay the groundwork for enabling access to .zfs snapshots via NFS clients. This patch makes the following core improvements. * All actively auto-mounted snapshots are now tracked in two global trees which are indexed by snapshot name and objset id respectively. This allows for fast lookups of any auto-mounted snapshot regardless without needing access to the parent dataset. * Snapshot entries are added to the tree in zfsctl_snapshot_mount(). However, they are now removed from the tree in the context of the unmount process. This eliminates the need complicated error logic in zfsctl_snapshot_unmount() to handle unmount failures. * References are now taken on the snapshot entries in the tree to ensure they always remain valid while a task is outstanding. * The MNT_SHRINKABLE flag is set on the snapshot vfsmount_t right after the auto-mount succeeds. This allows to kernel to unmount idle auto-mounted snapshots if needed removing the need for the zfsctl_unmount_snapshots() function. * Snapshots in active use will not be automatically unmounted. As long as at least one dentry is revalidated every zfs_expire_snapshot/2 seconds the auto-unmount expiration timer will be extended. * Commit torvalds/linux@bafc9b7 caused snapshots auto-mounted by ZFS to be immediately unmounted when the dentry was revalidated. This was a consequence of ZFS invaliding all snapdir dentries to ensure that negative dentries didn't mask new snapshots. This patch modifies the behavior such that only negative dentries are invalidated. This solves the issue and may result in a performance improvement. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3589 Closes #3344 Closes #3295 Closes #3257 Closes #3243 Closes #3030 Closes #2841
104 lines
3.8 KiB
C
104 lines
3.8 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
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* Copyright (C) 2011 Lawrence Livermore National Security, LLC.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* LLNL-CODE-403049.
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* Rewritten for Linux by:
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* Rohan Puri <rohan.puri15@gmail.com>
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* Brian Behlendorf <behlendorf1@llnl.gov>
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*/
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#ifndef _ZFS_CTLDIR_H
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#define _ZFS_CTLDIR_H
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#include <sys/vnode.h>
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#include <sys/pathname.h>
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#include <sys/zfs_vfsops.h>
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#include <sys/zfs_znode.h>
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#define ZFS_CTLDIR_NAME ".zfs"
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#define ZFS_SNAPDIR_NAME "snapshot"
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#define ZFS_SHAREDIR_NAME "shares"
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#define zfs_has_ctldir(zdp) \
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((zdp)->z_id == ZTOZSB(zdp)->z_root && \
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(ZTOZSB(zdp)->z_ctldir != NULL))
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#define zfs_show_ctldir(zdp) \
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(zfs_has_ctldir(zdp) && \
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(ZTOZSB(zdp)->z_show_ctldir))
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extern int zfs_expire_snapshot;
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/* zfsctl generic functions */
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extern int zfsctl_create(zfs_sb_t *zsb);
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extern void zfsctl_destroy(zfs_sb_t *zsb);
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extern struct inode *zfsctl_root(znode_t *zp);
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extern void zfsctl_init(void);
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extern void zfsctl_fini(void);
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extern boolean_t zfsctl_is_node(struct inode *ip);
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extern boolean_t zfsctl_is_snapdir(struct inode *ip);
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extern int zfsctl_fid(struct inode *ip, fid_t *fidp);
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/* zfsctl '.zfs' functions */
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extern int zfsctl_root_lookup(struct inode *dip, char *name,
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struct inode **ipp, int flags, cred_t *cr, int *direntflags,
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pathname_t *realpnp);
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/* zfsctl '.zfs/snapshot' functions */
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extern int zfsctl_snapdir_lookup(struct inode *dip, char *name,
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struct inode **ipp, int flags, cred_t *cr, int *direntflags,
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pathname_t *realpnp);
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extern int zfsctl_snapdir_rename(struct inode *sdip, char *sname,
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struct inode *tdip, char *tname, cred_t *cr, int flags);
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extern int zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr,
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int flags);
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extern int zfsctl_snapdir_mkdir(struct inode *dip, char *dirname, vattr_t *vap,
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struct inode **ipp, cred_t *cr, int flags);
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extern void zfsctl_snapdir_inactive(struct inode *ip);
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extern int zfsctl_snapshot_mount(struct path *path, int flags);
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extern int zfsctl_snapshot_unmount(char *snapname, int flags);
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extern int zfsctl_snapshot_unmount_delay(uint64_t objsetid, int delay);
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extern int zfsctl_lookup_objset(struct super_block *sb, uint64_t objsetid,
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zfs_sb_t **zsb);
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/* zfsctl '.zfs/shares' functions */
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extern int zfsctl_shares_lookup(struct inode *dip, char *name,
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struct inode **ipp, int flags, cred_t *cr, int *direntflags,
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pathname_t *realpnp);
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/*
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* These inodes numbers are reserved for the .zfs control directory.
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* It is important that they be no larger that 48-bits because only
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* 6 bytes are reserved in the NFS file handle for the object number.
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* However, they should be as large as possible to avoid conflicts
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* with the objects which are assigned monotonically by the dmu.
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*/
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#define ZFSCTL_INO_ROOT 0x0000FFFFFFFFFFFFULL
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#define ZFSCTL_INO_SHARES 0x0000FFFFFFFFFFFEULL
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#define ZFSCTL_INO_SNAPDIR 0x0000FFFFFFFFFFFDULL
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#define ZFSCTL_INO_SNAPDIRS 0x0000FFFFFFFFFFFCULL
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#define ZFSCTL_EXPIRE_SNAPSHOT 300
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#endif /* _ZFS_CTLDIR_H */
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