From 5943c611c47c9444e834555c867dec744158b7ad Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 22 Feb 2025 16:04:47 -0500 Subject: procfs: kill ->proc_dops It has two possible values - one for "forced lookup" entries, another for the normal ones. We'd be better off with that as an explicit flag anyway and in addition to that it opens some fun possibilities with ->d_op and ->d_flags handling. [moved PROC_ENTRY_FORCE_LOOKUP to include/linux/proc_fs.h, switched it to an unused bit - there was a conflict] Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/proc_fs.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index ea62201c74c4..de1d24f19f76 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -27,6 +27,8 @@ enum { PROC_ENTRY_proc_read_iter = 1U << 1, PROC_ENTRY_proc_compat_ioctl = 1U << 2, + + PROC_ENTRY_FORCE_LOOKUP = 1U << 7, }; struct proc_ops { -- cgit v1.2.3 From 790fa81b8c43cda9fe25c1b564d0afe3ddeeb370 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 24 Feb 2025 12:46:49 -0500 Subject: new helper: d_splice_alias_ops() Uses of d_set_d_op() on live dentry can be very dangerous; it is going to be withdrawn and replaced with saner things. The best way for a filesystem is to have the default dentry_operations set at mount time and be done with that - __d_alloc() will use that. Currently there are two cases when d_set_d_op() is used on a live dentry - one is procfs, which has several genuinely different dentry_operations instances (different ->d_revalidate(), etc.) and another is simple_lookup(), where we would be better off without overriding ->d_op. For procfs we have d_set_d_op() calls followed by d_splice_alias(); provide a new helper (d_splice_alias_ops(inode, dentry, d_ops)) that would combine those two, and do the d_set_d_op() part while under ->d_lock. That eliminates one of the places where ->d_flags had been modified without holding ->d_lock; current behaviour is not racy, but the reasons for that are far too brittle. Better move to uniform locking rules and simpler proof of correctness... The next commit will convert procfs to use of that helper; it is not exported and won't be until somebody comes up with convincing modular user for it. Again, the best approach is to have default ->d_op and let __d_alloc() do the right thing; filesystem _may_ need non-uniform ->d_op (procfs does), but there'd better be good reasons for that. Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/dcache.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index e29823c701ac..1993e6704552 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -245,6 +245,9 @@ extern struct dentry * d_alloc_anon(struct super_block *); extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, wait_queue_head_t *); extern struct dentry * d_splice_alias(struct inode *, struct dentry *); +/* weird procfs mess; *NOT* exported */ +extern struct dentry * d_splice_alias_ops(struct inode *, struct dentry *, + const struct dentry_operations *); extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, const struct qstr *name); -- cgit v1.2.3 From 05fb0e666495cda068c068a681ecbbf8e57324d0 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 23 Feb 2025 19:39:47 -0500 Subject: new helper: set_default_d_op() ... to be used instead of manually assigning to ->s_d_op. All in-tree filesystem converted (and field itself is renamed, so any out-of-tree ones in need of conversion will be caught by compiler). Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/dcache.h | 2 ++ include/linux/fs.h | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 1993e6704552..be7ae058fa90 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -607,4 +607,6 @@ static inline struct dentry *d_next_sibling(const struct dentry *dentry) return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); } +void set_default_d_op(struct super_block *, const struct dentry_operations *); + #endif /* __LINUX_DCACHE_H */ diff --git a/include/linux/fs.h b/include/linux/fs.h index 96c7925a6551..7cd8eaab4d4e 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1413,7 +1413,7 @@ struct super_block { */ const char *s_subtype; - const struct dentry_operations *s_d_op; /* default d_op for dentries */ + const struct dentry_operations *__s_d_op; /* default d_op for dentries */ struct shrinker *s_shrink; /* per-sb shrinker handle */ -- cgit v1.2.3 From 2fa8bf42c50582c7302918474aae8c52b59e7910 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 23 Feb 2025 19:53:00 -0500 Subject: set_default_d_op(): calculate the matching value for ->d_flags ... and store it in ->s_d_flags, to be used by __d_alloc() Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/fs.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index 7cd8eaab4d4e..65548e70e596 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1400,6 +1400,7 @@ struct super_block { char s_sysfs_name[UUID_STRING_LEN + 1]; unsigned int s_max_links; + unsigned int s_d_flags; /* default d_flags for dentries */ /* * The next field is for VFS *only*. No filesystems have any business -- cgit v1.2.3 From 691fb82ca6ccdcdb9e60e754b55659271d5280e7 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 23 Feb 2025 20:18:15 -0500 Subject: make d_set_d_op() static Convert the last user (d_alloc_pseudo()) and be done with that. Any out-of-tree filesystem using it should switch to d_splice_alias_ops() or, better yet, check whether it really needs to have ->d_op vary among its dentries. Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/dcache.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index be7ae058fa90..cc3e1c1a3454 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -237,7 +237,6 @@ extern void d_instantiate_new(struct dentry *, struct inode *); extern void __d_drop(struct dentry *dentry); extern void d_drop(struct dentry *dentry); extern void d_delete(struct dentry *); -extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); /* allocate/de-allocate */ extern struct dentry * d_alloc(struct dentry *, const struct qstr *); -- cgit v1.2.3 From 0b136e7d18fa8bb1251ab06f4f30e883da780245 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 23 Feb 2025 20:59:01 -0500 Subject: kill simple_dentry_operations No users left and anything that wants it would be better off just setting DCACHE_DONTCACHE in their ->s_d_flags. Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/fs.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index 65548e70e596..d58bbb8262e8 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3606,7 +3606,6 @@ extern const struct address_space_operations ram_aops; extern int always_delete_dentry(const struct dentry *); extern struct inode *alloc_anon_inode(struct super_block *); extern int simple_nosetlease(struct file *, int, struct file_lease **, void **); -extern const struct dentry_operations simple_dentry_operations; extern struct dentry *simple_lookup(struct inode *, struct dentry *, unsigned int flags); extern ssize_t generic_read_dir(struct file *, char __user *, size_t, loff_t *); -- cgit v1.2.3