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Don't pass inode to ->d_hash() and ->d_compare()

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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>
This commit is contained in:
Linus Torvalds
2013-05-21 15:22:44 -07:00
committed by Al Viro
parent 642b704cd7
commit da53be12bb
23 changed files with 108 additions and 165 deletions
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6
Documentation/filesystems/Locking
View File

@@ -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 *);

19
Documentation/filesystems/vfs.txt
View File

@@ -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.