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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-05-21 15:22:44 -0700 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2013-06-29 12:57:36 +0400 |
| commit | da53be12bbb4fabbe2e9f6f908de0cf478b5161d (patch) | |
| tree | a0436fb462a7b16c82e58336e17c55b814f7be6b /Documentation/filesystems/vfs.txt | |
| parent | 642b704cd7a29be0b8900971eb525086c1c995b7 (diff) | |
| download | linux-da53be12bbb4fabbe2e9f6f908de0cf478b5161d.tar.gz linux-da53be12bbb4fabbe2e9f6f908de0cf478b5161d.tar.bz2 linux-da53be12bbb4fabbe2e9f6f908de0cf478b5161d.zip | |
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/filesystems/vfs.txt')
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 19 |
1 files changed, 8 insertions, 11 deletions
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. |