c86243b090
Container folks are complaining that dnf/yum issues too many sync while installing packages and this slows down the image build. Build requirement is such that they don't care if a node goes down while build was still going on. In that case, they will simply throw away unfinished layer and start new build. So they don't care about syncing intermediate state to the disk and hence don't want to pay the price associated with sync. So they are asking for mount options where they can disable sync on overlay mount point. They primarily seem to have two use cases. - For building images, they will mount overlay with nosync and then sync upper layer after unmounting overlay and reuse upper as lower for next layer. - For running containers, they don't seem to care about syncing upper layer because if node goes down, they will simply throw away upper layer and create a fresh one. So this patch provides a mount option "volatile" which disables all forms of sync. Now it is caller's responsibility to throw away upper if system crashes or shuts down and start fresh. With "volatile", I am seeing roughly 20% speed up in my VM where I am just installing emacs in an image. Installation time drops from 31 seconds to 25 seconds when nosync option is used. This is for the case of building on top of an image where all packages are already cached. That way I take out the network operations latency out of the measurement. Giuseppe is also looking to cut down on number of iops done on the disk. He is complaining that often in cloud their VMs are throttled if they cross the limit. This option can help them where they reduce number of iops (by cutting down on frequent sync and writebacks). Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com> Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
143 lines
3.2 KiB
C
143 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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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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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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bool metacopy;
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bool ovl_volatile;
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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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/* Unusable (conflicting) uuid */
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bool bad_uuid;
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/* Used as a lower layer (but maybe also as upper) */
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bool is_lower;
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};
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struct ovl_layer {
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struct vfsmount *mnt;
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/* Trap in ovl inode cache */
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struct inode *trap;
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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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const 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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unsigned int numlayer;
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/* Number of unique fs among layers including upper fs */
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unsigned int numfs;
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const struct ovl_layer *layers;
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struct ovl_sb *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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bool share_whiteout;
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/* Traps in ovl inode cache */
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struct inode *workbasedir_trap;
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struct inode *workdir_trap;
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struct inode *indexdir_trap;
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/* -1: disabled, 0: same fs, 1..32: number of unused ino bits */
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int xino_mode;
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/* For allocation of non-persistent inode numbers */
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atomic_long_t last_ino;
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/* Whiteout dentry cache */
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struct dentry *whiteout;
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};
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static inline struct vfsmount *ovl_upper_mnt(struct ovl_fs *ofs)
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{
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return ofs->layers[0].mnt;
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}
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static inline struct ovl_fs *OVL_FS(struct super_block *sb)
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{
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return (struct ovl_fs *)sb->s_fs_info;
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}
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static inline bool ovl_should_sync(struct ovl_fs *ofs)
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{
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return !ofs->config.ovl_volatile;
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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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union {
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struct ovl_dir_cache *cache; /* directory */
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struct inode *lowerdata; /* regular file */
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};
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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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