forked from luck/tmp_suning_uos_patched
9bdebc2bd1
Currently, running into a shrink list that contains dentries from different
filesystems can cause several unpleasant things for shrink_dcache_parent()
and for umount(2).
The first problem is that there's a window during shrink_dentry_list() between
__dentry_kill() takes a victim out and dropping reference to its parent. During
that window the parent looks like a genuine busy dentry. shrink_dcache_parent()
(or, worse yet, shrink_dcache_for_umount()) coming at that time will see no
eviction candidates and no indication that it needs to wait for some
shrink_dentry_list() to proceed further.
That applies for any shrink list that might intersect with the subtree we are
trying to shrink; the only reason it does not blow on umount(2) in the mainline
is that we unregister the memory shrinker before hitting shrink_dcache_for_umount().
Another problem happens if something in a mixed-filesystem shrink list gets
be stuck in e.g. iput(), getting umount of unrelated fs to spin waiting for
the stuck shrinker to get around to our dentries.
Solution:
1) have shrink_dentry_list() decrement the parent's refcount and
make sure it's on a shrink list (ours unless it already had been on some
other) before calling __dentry_kill(). That eliminates the window when
shrink_dcache_parent() would've blown past the entire subtree without
noticing anything with zero refcount not on shrink lists.
2) when shrink_dcache_parent() has found no eviction candidates,
but some dentries are still sitting on shrink lists, rather than
repeating the scan in hope that shrinkers have progressed, scan looking
for something on shrink lists with zero refcount. If such a thing is
found, grab rcu_read_lock() and stop the scan, with caller locking
it for eviction, dropping out of RCU and doing __dentry_kill(), with
the same treatment for parent as shrink_dentry_list() would do.
Note that right now mixed-filesystem shrink lists do not occur, so this
is not a mainline bug. Howevere, there's a bunch of uses for such
beasts (e.g. the "try and evict everything we can out of given page"
patches; there are potential uses in mount-related code, considerably
simplifying the life in fs/namespace.c, etc.)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
201 lines
5.3 KiB
C
201 lines
5.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/* fs/ internal definitions
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*
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* Copyright (C) 2006 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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struct super_block;
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struct file_system_type;
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struct iomap;
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struct iomap_ops;
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struct linux_binprm;
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struct path;
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struct mount;
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struct shrink_control;
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struct fs_context;
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/*
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* block_dev.c
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*/
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#ifdef CONFIG_BLOCK
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extern void __init bdev_cache_init(void);
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extern int __sync_blockdev(struct block_device *bdev, int wait);
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#else
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static inline void bdev_cache_init(void)
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{
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}
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static inline int __sync_blockdev(struct block_device *bdev, int wait)
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{
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return 0;
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}
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#endif
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/*
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* buffer.c
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*/
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extern void guard_bio_eod(int rw, struct bio *bio);
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extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
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get_block_t *get_block, struct iomap *iomap);
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void __generic_write_end(struct inode *inode, loff_t pos, unsigned copied,
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struct page *page);
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/*
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* char_dev.c
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*/
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extern void __init chrdev_init(void);
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/*
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* fs_context.c
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*/
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extern const struct fs_context_operations legacy_fs_context_ops;
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extern int parse_monolithic_mount_data(struct fs_context *, void *);
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extern void fc_drop_locked(struct fs_context *);
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extern void vfs_clean_context(struct fs_context *fc);
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extern int finish_clean_context(struct fs_context *fc);
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/*
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* namei.c
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*/
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extern int filename_lookup(int dfd, struct filename *name, unsigned flags,
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struct path *path, struct path *root);
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extern int user_path_mountpoint_at(int, const char __user *, unsigned int, struct path *);
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extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
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const char *, unsigned int, struct path *);
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long do_mknodat(int dfd, const char __user *filename, umode_t mode,
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unsigned int dev);
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long do_mkdirat(int dfd, const char __user *pathname, umode_t mode);
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long do_rmdir(int dfd, const char __user *pathname);
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long do_unlinkat(int dfd, struct filename *name);
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long do_symlinkat(const char __user *oldname, int newdfd,
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const char __user *newname);
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int do_linkat(int olddfd, const char __user *oldname, int newdfd,
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const char __user *newname, int flags);
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/*
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* namespace.c
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*/
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extern void *copy_mount_options(const void __user *);
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extern char *copy_mount_string(const void __user *);
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extern struct vfsmount *lookup_mnt(const struct path *);
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extern int finish_automount(struct vfsmount *, struct path *);
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extern int sb_prepare_remount_readonly(struct super_block *);
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extern void __init mnt_init(void);
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extern int __mnt_want_write_file(struct file *);
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extern void __mnt_drop_write_file(struct file *);
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extern void dissolve_on_fput(struct vfsmount *);
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/*
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* fs_struct.c
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*/
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extern void chroot_fs_refs(const struct path *, const struct path *);
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/*
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* file_table.c
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*/
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extern struct file *alloc_empty_file(int, const struct cred *);
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extern struct file *alloc_empty_file_noaccount(int, const struct cred *);
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/*
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* super.c
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*/
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extern int reconfigure_super(struct fs_context *);
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extern bool trylock_super(struct super_block *sb);
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extern struct super_block *user_get_super(dev_t);
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/*
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* open.c
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*/
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struct open_flags {
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int open_flag;
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umode_t mode;
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int acc_mode;
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int intent;
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int lookup_flags;
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};
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extern struct file *do_filp_open(int dfd, struct filename *pathname,
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const struct open_flags *op);
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extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
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const char *, const struct open_flags *);
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long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
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long do_faccessat(int dfd, const char __user *filename, int mode);
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int do_fchmodat(int dfd, const char __user *filename, umode_t mode);
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int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
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int flag);
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extern int vfs_open(const struct path *, struct file *);
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/*
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* inode.c
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*/
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extern long prune_icache_sb(struct super_block *sb, struct shrink_control *sc);
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extern void inode_add_lru(struct inode *inode);
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extern int dentry_needs_remove_privs(struct dentry *dentry);
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/*
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* fs-writeback.c
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*/
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extern void inode_io_list_del(struct inode *inode);
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extern long get_nr_dirty_inodes(void);
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extern int invalidate_inodes(struct super_block *, bool);
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/*
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* dcache.c
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*/
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extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
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extern int d_set_mounted(struct dentry *dentry);
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extern long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc);
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extern struct dentry *d_alloc_cursor(struct dentry *);
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extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
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extern void dput_to_list(struct dentry *, struct list_head *);
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extern void shrink_dentry_list(struct list_head *);
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/*
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* read_write.c
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*/
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extern int rw_verify_area(int, struct file *, const loff_t *, size_t);
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/*
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* pipe.c
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*/
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extern const struct file_operations pipefifo_fops;
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/*
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* fs_pin.c
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*/
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extern void group_pin_kill(struct hlist_head *p);
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extern void mnt_pin_kill(struct mount *m);
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/*
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* fs/nsfs.c
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*/
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extern const struct dentry_operations ns_dentry_operations;
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/*
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* fs/ioctl.c
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*/
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extern int do_vfs_ioctl(struct file *file, unsigned int fd, unsigned int cmd,
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unsigned long arg);
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/*
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* iomap support:
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*/
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typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
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void *data, struct iomap *iomap);
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loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length,
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unsigned flags, const struct iomap_ops *ops, void *data,
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iomap_actor_t actor);
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/* direct-io.c: */
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int sb_init_dio_done_wq(struct super_block *sb);
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