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authorLinus Torvalds <torvalds@linux-foundation.org>2013-05-21 15:22:44 -0700
committerAl Viro <viro@zeniv.linux.org.uk>2013-06-29 12:57:36 +0400
commitda53be12bbb4fabbe2e9f6f908de0cf478b5161d (patch)
treea0436fb462a7b16c82e58336e17c55b814f7be6b /Documentation
parent642b704cd7a29be0b8900971eb525086c1c995b7 (diff)
Don't pass inode to ->d_hash() and ->d_compare()
Instances either don't look at it at all (the majority of cases) or only want it to find the superblock (which can be had as dentry->d_sb). A few cases that want more are actually safe with dentry->d_inode - the only precaution needed is the check that it hadn't been replaced with NULL by rmdir() or by overwriting rename(), which case should be simply treated as cache miss. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/Locking6
-rw-r--r--Documentation/filesystems/vfs.txt19
2 files changed, 10 insertions, 15 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index bdd82b2339d9..f94a362f408e 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -11,10 +11,8 @@ be able to use diff(1).
prototypes:
int (*d_revalidate)(struct dentry *, unsigned int);
int (*d_weak_revalidate)(struct dentry *, unsigned int);
- int (*d_hash)(const struct dentry *, const struct inode *,
- struct qstr *);
- int (*d_compare)(const struct dentry *, const struct inode *,
- const struct dentry *, const struct inode *,
+ int (*d_hash)(const struct dentry *, struct qstr *);
+ int (*d_compare)(const struct dentry *, const struct dentry *,
unsigned int, const char *, const struct qstr *);
int (*d_delete)(struct dentry *);
void (*d_release)(struct dentry *);
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 4a35f6614a66..51ba44e3fc40 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -901,10 +901,8 @@ defined:
struct dentry_operations {
int (*d_revalidate)(struct dentry *, unsigned int);
int (*d_weak_revalidate)(struct dentry *, unsigned int);
- int (*d_hash)(const struct dentry *, const struct inode *,
- struct qstr *);
- int (*d_compare)(const struct dentry *, const struct inode *,
- const struct dentry *, const struct inode *,
+ int (*d_hash)(const struct dentry *, struct qstr *);
+ int (*d_compare)(const struct dentry *, const struct dentry *,
unsigned int, const char *, const struct qstr *);
int (*d_delete)(const struct dentry *);
void (*d_release)(struct dentry *);
@@ -949,25 +947,24 @@ struct dentry_operations {
d_hash: called when the VFS adds a dentry to the hash table. The first
dentry passed to d_hash is the parent directory that the name is
- to be hashed into. The inode is the dentry's inode.
+ to be hashed into.
Same locking and synchronisation rules as d_compare regarding
what is safe to dereference etc.
d_compare: called to compare a dentry name with a given name. The first
dentry is the parent of the dentry to be compared, the second is
- the parent's inode, then the dentry and inode (may be NULL) of the
- child dentry. len and name string are properties of the dentry to be
- compared. qstr is the name to compare it with.
+ the child dentry. len and name string are properties of the dentry
+ to be compared. qstr is the name to compare it with.
Must be constant and idempotent, and should not take locks if
- possible, and should not or store into the dentry or inodes.
- Should not dereference pointers outside the dentry or inodes without
+ possible, and should not or store into the dentry.
+ Should not dereference pointers outside the dentry without
lots of care (eg. d_parent, d_inode, d_name should not be used).
However, our vfsmount is pinned, and RCU held, so the dentries and
inodes won't disappear, neither will our sb or filesystem module.
- ->i_sb and ->d_sb may be used.
+ ->d_sb may be used.
It is a tricky calling convention because it needs to be called under
"rcu-walk", ie. without any locks or references on things.