From acfde6e8abee6b23e53b08606f861d9124288030 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 4 Nov 2023 00:10:18 -0400 Subject: struct dentry: get rid of randomize_layout idiocy This is beyond ridiculous. There is a reason why that thing is cacheline-aligned... Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/dcache.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 3da2f0545d5d..1d9f7f132055 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -111,7 +111,7 @@ struct dentry { struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ struct rcu_head d_rcu; } d_u; -} __randomize_layout; +}; /* * dentry->d_lock spinlock nesting subclasses: -- cgit v1.2.3 From 641c3ef5cb68a1426d42e6d3aba16db9bdfbe94f Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Nov 2023 12:46:30 -0500 Subject: DCACHE_... ->d_flags bits: switch to BIT() For bits 20..22 (inode type cached in ->d_flags) turn the definitions into expressions like (5 << 20); everything else turns into straight use of BIT() Signed-off-by: Al Viro --- include/linux/dcache.h | 76 +++++++++++++++++++++++++------------------------- 1 file changed, 38 insertions(+), 38 deletions(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 1d9f7f132055..d9c314cc93b8 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -151,13 +151,13 @@ struct dentry_operations { */ /* d_flags entries */ -#define DCACHE_OP_HASH 0x00000001 -#define DCACHE_OP_COMPARE 0x00000002 -#define DCACHE_OP_REVALIDATE 0x00000004 -#define DCACHE_OP_DELETE 0x00000008 -#define DCACHE_OP_PRUNE 0x00000010 +#define DCACHE_OP_HASH BIT(0) +#define DCACHE_OP_COMPARE BIT(1) +#define DCACHE_OP_REVALIDATE BIT(2) +#define DCACHE_OP_DELETE BIT(3) +#define DCACHE_OP_PRUNE BIT(4) -#define DCACHE_DISCONNECTED 0x00000020 +#define DCACHE_DISCONNECTED BIT(5) /* This dentry is possibly not currently connected to the dcache tree, in * which case its parent will either be itself, or will have this flag as * well. nfsd will not use a dentry with this bit set, but will first @@ -168,50 +168,50 @@ struct dentry_operations { * dentry into place and return that dentry rather than the passed one, * typically using d_splice_alias. */ -#define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ +#define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */ -#define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */ +#define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ -#define DCACHE_CANT_MOUNT 0x00000100 -#define DCACHE_GENOCIDE 0x00000200 -#define DCACHE_SHRINK_LIST 0x00000400 +#define DCACHE_CANT_MOUNT BIT(8) +#define DCACHE_GENOCIDE BIT(9) +#define DCACHE_SHRINK_LIST BIT(10) -#define DCACHE_OP_WEAK_REVALIDATE 0x00000800 +#define DCACHE_OP_WEAK_REVALIDATE BIT(11) -#define DCACHE_NFSFS_RENAMED 0x00001000 +#define DCACHE_NFSFS_RENAMED BIT(12) /* this dentry has been "silly renamed" and has to be deleted on the last * dput() */ -#define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ -#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 +#define DCACHE_COOKIE BIT(13) /* For use by dcookie subsystem */ +#define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14) /* Parent inode is watched by some fsnotify listener */ -#define DCACHE_DENTRY_KILLED 0x00008000 +#define DCACHE_DENTRY_KILLED BIT(15) -#define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ -#define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ -#define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ +#define DCACHE_MOUNTED BIT(16) /* is a mountpoint */ +#define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */ +#define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */ #define DCACHE_MANAGED_DENTRY \ (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) -#define DCACHE_LRU_LIST 0x00080000 - -#define DCACHE_ENTRY_TYPE 0x00700000 -#define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ -#define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ -#define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ -#define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ -#define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ -#define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ -#define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ - -#define DCACHE_MAY_FREE 0x00800000 -#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ -#define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */ -#define DCACHE_OP_REAL 0x04000000 - -#define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ -#define DCACHE_DENTRY_CURSOR 0x20000000 -#define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */ +#define DCACHE_LRU_LIST BIT(19) + +#define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */ +#define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry (maybe fallthru to nowhere) */ +#define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */ +#define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */ +#define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */ +#define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type (or fallthru to such) */ +#define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type (or fallthru to such) */ +#define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink (or fallthru to such) */ + +#define DCACHE_MAY_FREE BIT(23) +#define DCACHE_FALLTHRU BIT(24) /* Fall through to lower layer */ +#define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ +#define DCACHE_OP_REAL BIT(26) + +#define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */ +#define DCACHE_DENTRY_CURSOR BIT(29) +#define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */ extern seqlock_t rename_lock; -- cgit v1.2.3 From 0bec65a80f1b1ebcda05286e539a204713b70353 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Nov 2023 12:50:29 -0500 Subject: DCACHE_COOKIE: RIP the last user gone in 2021... Signed-off-by: Al Viro --- include/linux/dcache.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index d9c314cc93b8..92c0b2a1ae2e 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -181,7 +181,6 @@ struct dentry_operations { #define DCACHE_NFSFS_RENAMED BIT(12) /* this dentry has been "silly renamed" and has to be deleted on the last * dput() */ -#define DCACHE_COOKIE BIT(13) /* For use by dcookie subsystem */ #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14) /* Parent inode is watched by some fsnotify listener */ -- cgit v1.2.3 From 8219cb58feddcf28909072015f4e17e29f68c41a Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Nov 2023 14:32:05 -0500 Subject: kill d_{is,set}_fallthru() Introduced in 2015 and never had any in-tree users... Signed-off-by: Al Viro --- include/linux/dcache.h | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 92c0b2a1ae2e..8cd937bb2292 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -195,16 +195,15 @@ struct dentry_operations { #define DCACHE_LRU_LIST BIT(19) #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */ -#define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry (maybe fallthru to nowhere) */ +#define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */ #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */ #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */ #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */ -#define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type (or fallthru to such) */ -#define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type (or fallthru to such) */ -#define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink (or fallthru to such) */ +#define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */ +#define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */ +#define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */ #define DCACHE_MAY_FREE BIT(23) -#define DCACHE_FALLTHRU BIT(24) /* Fall through to lower layer */ #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ #define DCACHE_OP_REAL BIT(26) @@ -489,14 +488,6 @@ static inline int simple_positive(const struct dentry *dentry) return d_really_is_positive(dentry) && !d_unhashed(dentry); } -extern void d_set_fallthru(struct dentry *dentry); - -static inline bool d_is_fallthru(const struct dentry *dentry) -{ - return dentry->d_flags & DCACHE_FALLTHRU; -} - - extern int sysctl_vfs_cache_pressure; static inline unsigned long vfs_pressure_ratio(unsigned long val) -- cgit v1.2.3 From 0d486510f86eb8162022ed61e6dc424a10909a10 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Nov 2023 15:22:40 -0500 Subject: dentry.h: trim externs d_instantiate_unique() had been gone for 7 years; __d_lookup...() and shrink_dcache_for_umount() are fs/internal.h fodder. Signed-off-by: Al Viro --- include/linux/dcache.h | 5 ----- 1 file changed, 5 deletions(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 8cd937bb2292..9706bf1dc5de 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -218,7 +218,6 @@ extern seqlock_t rename_lock; */ extern void d_instantiate(struct dentry *, struct inode *); extern void d_instantiate_new(struct dentry *, struct inode *); -extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); extern void __d_drop(struct dentry *dentry); extern void d_drop(struct dentry *dentry); @@ -240,7 +239,6 @@ extern struct dentry * d_obtain_alias(struct inode *); extern struct dentry * d_obtain_root(struct inode *); extern void shrink_dcache_sb(struct super_block *); extern void shrink_dcache_parent(struct dentry *); -extern void shrink_dcache_for_umount(struct super_block *); extern void d_invalidate(struct dentry *); /* only used at mount-time */ @@ -275,9 +273,6 @@ extern struct dentry *d_ancestor(struct dentry *, struct dentry *); /* appendix may either be NULL or be used for transname suffixes */ extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); -extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); -extern struct dentry *__d_lookup_rcu(const struct dentry *parent, - const struct qstr *name, unsigned *seq); static inline unsigned d_count(const struct dentry *dentry) { -- cgit v1.2.3 From 2fcd38f4de7256e2b5cb23ad22a6e3ebfea7dd18 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Nov 2023 15:24:45 -0500 Subject: [software coproarchaeology] dentry.h: kill a mysterious comment there's a strange comment in front of d_lookup() declaration: /* appendix may either be NULL or be used for transname suffixes */ Looks like nobody had been curious enough to track its history; it predates git, it predates bitkeeper and if you look through the pre-BK trees, you finally arrive at this in 2.1.44-for-davem: /* appendix may either be NULL or be used for transname suffixes */ -extern struct dentry * d_lookup(struct inode * dir, struct qstr * name, - struct qstr * appendix); +extern struct dentry * d_lookup(struct dentry * dir, struct qstr * name); In other words, it refers to the third argument d_lookup() used to have back then. It had been introduced in 2.1.43-pre, on June 12 1997, along with d_lookup(), only to be removed by July 4 1997, presumably when the Cthulhu-awful thing it used to be used for (look for CONFIG_TRANS_NAMES in 2.1.43-pre, and keep a heavy-duty barfbag ready) had been, er, noticed and recognized for what it had been. Despite the appendectomy, the comment remained. Some things really need to be put out of their misery... Signed-off-by: Al Viro --- include/linux/dcache.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 9706bf1dc5de..a5e5e274eee0 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -270,7 +270,6 @@ extern void d_move(struct dentry *, struct dentry *); extern void d_exchange(struct dentry *, struct dentry *); extern struct dentry *d_ancestor(struct dentry *, struct dentry *); -/* appendix may either be NULL or be used for transname suffixes */ extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); -- cgit v1.2.3 From 698f1e2b71736977b04f951e2e2ef1c9a80696ff Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Nov 2023 16:19:59 -0500 Subject: kill d_backing_dentry() no users left Signed-off-by: Al Viro --- include/linux/dcache.h | 15 --------------- 1 file changed, 15 deletions(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index a5e5e274eee0..fa0414cff85c 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -530,21 +530,6 @@ static inline struct inode *d_backing_inode(const struct dentry *upper) return inode; } -/** - * d_backing_dentry - Get upper or lower dentry we should be using - * @upper: The upper layer - * - * This is the helper that should be used to get the dentry of the inode that - * will be used if this dentry were opened as a file. It may be the upper - * dentry or it may be a lower dentry pinned by the upper. - * - * Normal filesystems should not use this to access their own dentries. - */ -static inline struct dentry *d_backing_dentry(struct dentry *upper) -{ - return upper; -} - /** * d_real - Return the real dentry * @dentry: the dentry to query -- cgit v1.2.3 From da549bdd15c295c24b2ee7ffe7ad0f3877fa8a87 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 7 Nov 2023 02:00:39 -0500 Subject: dentry: switch the lists of children to hlist Saves a pointer per struct dentry and actually makes the things less clumsy. Cleaned the d_walk() and dcache_readdir() a bit by use of hlist_for_... iterators. A couple of new helpers - d_first_child() and d_next_sibling(), to make the expressions less awful. Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- include/linux/dcache.h | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 3da2f0545d5d..0e397a0c519c 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -68,12 +68,12 @@ extern const struct qstr dotdot_name; * large memory footprint increase). */ #ifdef CONFIG_64BIT -# define DNAME_INLINE_LEN 32 /* 192 bytes */ +# define DNAME_INLINE_LEN 40 /* 192 bytes */ #else # ifdef CONFIG_SMP -# define DNAME_INLINE_LEN 36 /* 128 bytes */ -# else # define DNAME_INLINE_LEN 40 /* 128 bytes */ +# else +# define DNAME_INLINE_LEN 44 /* 128 bytes */ # endif #endif @@ -101,8 +101,8 @@ struct dentry { struct list_head d_lru; /* LRU list */ wait_queue_head_t *d_wait; /* in-lookup ones only */ }; - struct list_head d_child; /* child of parent list */ - struct list_head d_subdirs; /* our children */ + struct hlist_node d_sib; /* child of parent list */ + struct hlist_head d_children; /* our children */ /* * d_alias and d_rcu can share memory */ @@ -600,4 +600,14 @@ struct name_snapshot { void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); void release_dentry_name_snapshot(struct name_snapshot *); +static inline struct dentry *d_first_child(const struct dentry *dentry) +{ + return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); +} + +static inline struct dentry *d_next_sibling(const struct dentry *dentry) +{ + return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); +} + #endif /* __LINUX_DCACHE_H */ -- cgit v1.2.3 From f2824db1b49f947ba6e208ddf02edf4b1391480a Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 18 Nov 2023 16:42:43 -0500 Subject: kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller now that the only user of d_instantiate_anon() is gone... [braino fix folded - kudos to Dan Carpenter] Signed-off-by: Al Viro --- include/linux/dcache.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index fa0414cff85c..8c5e3bdf1147 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -218,7 +218,6 @@ extern seqlock_t rename_lock; */ extern void d_instantiate(struct dentry *, struct inode *); extern void d_instantiate_new(struct dentry *, struct inode *); -extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); extern void __d_drop(struct dentry *dentry); extern void d_drop(struct dentry *dentry); extern void d_delete(struct dentry *); -- cgit v1.2.3 From 8a54b38f3e5ced6cc4b246b8e54bd0f50deceaa8 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 11 Nov 2023 16:01:27 -0500 Subject: d_genocide(): move the extern into fs/internal.h Signed-off-by: Al Viro --- include/linux/dcache.h | 3 --- 1 file changed, 3 deletions(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 8c5e3bdf1147..b4324d47f249 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -243,9 +243,6 @@ extern void d_invalidate(struct dentry *); /* only used at mount-time */ extern struct dentry * d_make_root(struct inode *); -/* - the ramfs-type tree */ -extern void d_genocide(struct dentry *); - extern void d_mark_tmpfile(struct file *, struct inode *); extern void d_tmpfile(struct file *, struct inode *); -- cgit v1.2.3 From 57851607326a2beef21e67f83f4f53a90df8445a Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 12 Nov 2023 21:38:48 -0500 Subject: get rid of DCACHE_GENOCIDE ... now that we never call d_genocide() other than from kill_litter_super() Signed-off-by: Al Viro --- include/linux/dcache.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index b4324d47f249..981f529c6cb5 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -173,7 +173,6 @@ struct dentry_operations { #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ #define DCACHE_CANT_MOUNT BIT(8) -#define DCACHE_GENOCIDE BIT(9) #define DCACHE_SHRINK_LIST BIT(10) #define DCACHE_OP_WEAK_REVALIDATE BIT(11) -- cgit v1.2.3 From 1b327b5ac57cf83e3d015de45d0142852f475375 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Nov 2023 14:07:43 -0500 Subject: kill DCACHE_MAY_FREE With the new ordering in __dentry_kill() it has become redundant - it's set if and only if both DCACHE_DENTRY_KILLED and DCACHE_SHRINK_LIST are set. We set it in __dentry_kill(), after having set DCACHE_DENTRY_KILLED with the only condition being that DCACHE_SHRINK_LIST is there; all of that is done without dropping ->d_lock and the only place that checks that flag (shrink_dentry_list()) does so under ->d_lock, after having found the victim on its shrink list. Since DCACHE_SHRINK_LIST is set only when placing dentry into shrink list and removed only by shrink_dentry_list() itself, a check for DCACHE_DENTRY_KILLED in there would be equivalent to check for DCACHE_MAY_FREE. Signed-off-by: Al Viro --- include/linux/dcache.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index b4449a1a47ff..48b393545ec2 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -202,7 +202,6 @@ struct dentry_operations { #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */ #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */ -#define DCACHE_MAY_FREE BIT(23) #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ #define DCACHE_OP_REAL BIT(26) -- cgit v1.2.3 From 1b6ae9f6e6c3e3c35aad0f11b116a81780b8aa03 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Mon, 6 Nov 2023 14:44:17 +0100 Subject: dcache: remove unnecessary NULL check in dget_dlock() dget_dlock() requires dentry->d_lock to be held when called, yet contains a NULL check for dentry. An audit of all calls to dget_dlock() shows that it is never called with a NULL pointer (as spin_lock()/spin_unlock() would crash in these cases): $ git grep -W '\' arch/powerpc/platforms/cell/spufs/inode.c- spin_lock(&dentry->d_lock); arch/powerpc/platforms/cell/spufs/inode.c- if (simple_positive(dentry)) { arch/powerpc/platforms/cell/spufs/inode.c: dget_dlock(dentry); fs/autofs/expire.c- spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); fs/autofs/expire.c- if (simple_positive(child)) { fs/autofs/expire.c: dget_dlock(child); fs/autofs/root.c: dget_dlock(active); fs/autofs/root.c- spin_unlock(&active->d_lock); fs/autofs/root.c: dget_dlock(expiring); fs/autofs/root.c- spin_unlock(&expiring->d_lock); fs/ceph/dir.c- if (!spin_trylock(&dentry->d_lock)) fs/ceph/dir.c- continue; [...] fs/ceph/dir.c: dget_dlock(dentry); fs/ceph/mds_client.c- spin_lock(&alias->d_lock); [...] fs/ceph/mds_client.c: dn = dget_dlock(alias); fs/configfs/inode.c- spin_lock(&dentry->d_lock); fs/configfs/inode.c- if (simple_positive(dentry)) { fs/configfs/inode.c: dget_dlock(dentry); fs/libfs.c: found = dget_dlock(d); fs/libfs.c- spin_unlock(&d->d_lock); fs/libfs.c: found = dget_dlock(child); fs/libfs.c- spin_unlock(&child->d_lock); fs/libfs.c: child = dget_dlock(d); fs/libfs.c- spin_unlock(&d->d_lock); fs/ocfs2/dcache.c: dget_dlock(dentry); fs/ocfs2/dcache.c- spin_unlock(&dentry->d_lock); include/linux/dcache.h:static inline struct dentry *dget_dlock(struct dentry *dentry) After taking out the NULL check, dget_dlock() becomes almost identical to __dget_dlock(); the only difference is that dget_dlock() returns the dentry that was passed in. These are static inline helpers, so we can rely on the compiler to discard unused return values. We can therefore also remove __dget_dlock() and replace calls to it by dget_dlock(). Also fix up and improve the kerneldoc comments while we're at it. Al Viro pointed out that we can also clean up some of the callers to make use of the returned value and provided a bit more info for the kerneldoc. While preparing v2 I also noticed that the tabs used in the kerneldoc comments were causing the kerneldoc to get parsed incorrectly so I also fixed this up (including for d_unhashed, which is otherwise unrelated). Testing: x86 defconfig build + boot; make htmldocs for the kerneldoc warning. objdump shows there are code generation changes. Link: https://lore.kernel.org/all/20231022164520.915013-1-vegard.nossum@oracle.com/ Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: Nick Piggin Cc: Waiman Long Cc: linux-doc@vger.kernel.org Signed-off-by: Vegard Nossum Signed-off-by: Al Viro --- include/linux/dcache.h | 41 ++++++++++++++++++++++++++++++----------- 1 file changed, 30 insertions(+), 11 deletions(-) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 48b393545ec2..1666c387861f 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -287,20 +287,40 @@ extern char *dentry_path(const struct dentry *, char *, int); /* Allocation counts.. */ /** - * dget, dget_dlock - get a reference to a dentry - * @dentry: dentry to get a reference to + * dget_dlock - get a reference to a dentry + * @dentry: dentry to get a reference to * - * Given a dentry or %NULL pointer increment the reference count - * if appropriate and return the dentry. A dentry will not be - * destroyed when it has references. + * Given a live dentry, increment the reference count and return the dentry. + * Caller must hold @dentry->d_lock. Making sure that dentry is alive is + * caller's resonsibility. There are many conditions sufficient to guarantee + * that; e.g. anything with non-negative refcount is alive, so's anything + * hashed, anything positive, anyone's parent, etc. */ static inline struct dentry *dget_dlock(struct dentry *dentry) { - if (dentry) - dentry->d_lockref.count++; + dentry->d_lockref.count++; return dentry; } + +/** + * dget - get a reference to a dentry + * @dentry: dentry to get a reference to + * + * Given a dentry or %NULL pointer increment the reference count + * if appropriate and return the dentry. A dentry will not be + * destroyed when it has references. Conversely, a dentry with + * no references can disappear for any number of reasons, starting + * with memory pressure. In other words, that primitive is + * used to clone an existing reference; using it on something with + * zero refcount is a bug. + * + * NOTE: it will spin if @dentry->d_lock is held. From the deadlock + * avoidance point of view it is equivalent to spin_lock()/increment + * refcount/spin_unlock(), so calling it under @dentry->d_lock is + * always a bug; so's calling it under ->d_lock on any of its descendents. + * + */ static inline struct dentry *dget(struct dentry *dentry) { if (dentry) @@ -311,12 +331,11 @@ static inline struct dentry *dget(struct dentry *dentry) extern struct dentry *dget_parent(struct dentry *dentry); /** - * d_unhashed - is dentry hashed - * @dentry: entry to check + * d_unhashed - is dentry hashed + * @dentry: entry to check * - * Returns true if the dentry passed is not currently hashed. + * Returns true if the dentry passed is not currently hashed. */ - static inline int d_unhashed(const struct dentry *dentry) { return hlist_bl_unhashed(&dentry->d_hash); -- cgit v1.2.3