forked from luck/tmp_suning_uos_patched
795939a93e
With mount option "xino=on", mounter declares that there are enough free high bits in underlying fs to hold the layer fsid. If overlayfs does encounter underlying inodes using the high xino bits reserved for layer fsid, a warning will be emitted and the original inode number will be used. The mount option name "xino" goes after a similar meaning mount option of aufs, but in overlayfs case, the mapping is stateless. An example for a use case of "xino=on" is when upper/lower is on an xfs filesystem. xfs uses 64bit inode numbers, but it currently never uses the upper 8bit for inode numbers exposed via stat(2) and that is not likely to change in the future without user opting-in for a new xfs feature. The actual number of unused upper bit is much larger and determined by the xfs filesystem geometry (64 - agno_log - agblklog - inopblog). That means that for all practical purpose, there are enough unused bits in xfs inode numbers for more than OVL_MAX_STACK unique fsid's. Another use case of "xino=on" is when upper/lower is on tmpfs. tmpfs inode numbers are allocated sequentially since boot, so they will practially never use the high inode number bits. For compatibility with applications that expect 32bit inodes, the feature can be disabled with "xino=off". The option "xino=auto" automatically detects underlying filesystem that use 32bit inodes and enables the feature. The Kconfig option OVERLAY_FS_XINO_AUTO and module parameter of the same name, determine if the default mode for overlayfs mount is "xino=auto" or "xino=off". Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
112 lines
2.6 KiB
C
112 lines
2.6 KiB
C
/*
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*
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* Copyright (C) 2011 Novell Inc.
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* Copyright (C) 2016 Red Hat, Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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struct ovl_config {
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char *lowerdir;
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char *upperdir;
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char *workdir;
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bool default_permissions;
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bool redirect_dir;
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bool redirect_follow;
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const char *redirect_mode;
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bool index;
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bool nfs_export;
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int xino;
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};
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struct ovl_sb {
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struct super_block *sb;
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dev_t pseudo_dev;
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};
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struct ovl_layer {
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struct vfsmount *mnt;
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struct ovl_sb *fs;
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/* Index of this layer in fs root (upper idx == 0) */
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int idx;
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/* One fsid per unique underlying sb (upper fsid == 0) */
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int fsid;
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};
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struct ovl_path {
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struct ovl_layer *layer;
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struct dentry *dentry;
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};
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/* private information held for overlayfs's superblock */
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struct ovl_fs {
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struct vfsmount *upper_mnt;
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unsigned int numlower;
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/* Number of unique lower sb that differ from upper sb */
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unsigned int numlowerfs;
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struct ovl_layer *lower_layers;
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struct ovl_sb *lower_fs;
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/* workbasedir is the path at workdir= mount option */
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struct dentry *workbasedir;
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/* workdir is the 'work' directory under workbasedir */
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struct dentry *workdir;
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/* index directory listing overlay inodes by origin file handle */
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struct dentry *indexdir;
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long namelen;
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/* pathnames of lower and upper dirs, for show_options */
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struct ovl_config config;
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/* creds of process who forced instantiation of super block */
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const struct cred *creator_cred;
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bool tmpfile;
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bool noxattr;
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/* Did we take the inuse lock? */
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bool upperdir_locked;
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bool workdir_locked;
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/* Inode numbers in all layers do not use the high xino_bits */
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unsigned int xino_bits;
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};
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/* private information held for every overlayfs dentry */
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struct ovl_entry {
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union {
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struct {
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unsigned long flags;
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};
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struct rcu_head rcu;
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};
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unsigned numlower;
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struct ovl_path lowerstack[];
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};
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struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
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static inline struct ovl_entry *OVL_E(struct dentry *dentry)
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{
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return (struct ovl_entry *) dentry->d_fsdata;
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}
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struct ovl_inode {
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struct ovl_dir_cache *cache;
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const char *redirect;
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u64 version;
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unsigned long flags;
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struct inode vfs_inode;
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struct dentry *__upperdentry;
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struct inode *lower;
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/* synchronize copy up and more */
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struct mutex lock;
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};
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static inline struct ovl_inode *OVL_I(struct inode *inode)
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{
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return container_of(inode, struct ovl_inode, vfs_inode);
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}
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static inline struct dentry *ovl_upperdentry_dereference(struct ovl_inode *oi)
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{
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return READ_ONCE(oi->__upperdentry);
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}
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