Here is a different approach to the problem of i_ino uniqueness. Again,
I'll refer to my original email and patch for a description of the
problem...
With this patch, I'm taking the approach of only assigning out an i_ino
value when it's actually needed. This adds a lazy_getattr function. If
i_ino is 0, then this does an iunique and hashes the inode before doing
the actual getattr.
This patch is still a proof-of-concept. For a "real" patch, we'd need to:
1) add lazy functions for readdir and encode_fh (maybe also others)
2) clean up how root inode i_ino values are handled in superblocks
3) probably just have new_inode not have a counter, so that new inodes
created by it always get i_ino=0
4) convert all callers of new_inode that don't have a scheme to ensure
uniqueness
This patch does hash inodes in the standard way, but the lazy
approach could also be combined with the earlier patch I posted that
uses IDR, or a different hashing scheme that keeps these out of the
normal inode_hashtable. I figured I'd go with the approach of not adding
more infrastructure than was necessary as a first stab.
If this general approach seems alright, then could someone confirm
whether using generic_delete_inode as the drop_inode function is OK, or
whether I need to have pipefs actually handle the nlink counter
correctly and use generic_drop_inode?
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
diff --git a/fs/inode.c b/fs/inode.c
index 26cdb11..9d7da59 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -524,7 +524,7 @@ repeat:
*/
struct inode *new_inode(struct super_block *sb)
{
- static unsigned long last_ino;
+ static unsigned int last_ino;
struct inode * inode;
spin_lock_prefetch(&inode_lock);
@@ -683,7 +683,7 @@ static unsigned long hash(struct super_b
*/
ino_t iunique(struct super_block *sb, ino_t max_reserved)
{
- static ino_t counter;
+ static unsigned int counter;
struct inode *inode;
struct hlist_head * head;
ino_t res;
diff --git a/fs/libfs.c b/fs/libfs.c
index bd08e0e..75f8371 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -20,6 +20,18 @@ int simple_getattr(struct vfsmount *mnt,
return 0;
}
+/* same as simple_getattr, but get a unique inode number and hash the inode
+ * prior to doing the getattr */
+int lazy_getattr(struct vfsmount *mnt, struct dentry *dentry,
+ struct kstat *stat)
+{
+ if (dentry->d_inode->i_ino == 0) {
+ dentry->d_inode->i_ino = iunique(dentry->d_sb, 0);
+ insert_inode_hash(dentry->d_inode);
+ }
+ return simple_getattr(mnt, dentry, stat);
+}
+
int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
{
buf->f_type = dentry->d_sb->s_magic;
@@ -639,3 +651,4 @@ EXPORT_SYMBOL_GPL(simple_attr_open);
EXPORT_SYMBOL_GPL(simple_attr_close);
EXPORT_SYMBOL_GPL(simple_attr_read);
EXPORT_SYMBOL_GPL(simple_attr_write);
+EXPORT_SYMBOL_GPL(lazy_getattr);
diff --git a/fs/pipe.c b/fs/pipe.c
index b1626f2..6910081 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -837,6 +837,10 @@ static struct dentry_operations pipefs_d
.d_delete = pipefs_delete_dentry,
};
+static struct inode_operations pipefs_inode_operations = {
+ .getattr = lazy_getattr,
+};
+
static struct inode * get_pipe_inode(void)
{
struct inode *inode = new_inode(pipe_mnt->mnt_sb);
@@ -845,6 +849,10 @@ static struct inode * get_pipe_inode(voi
if (!inode)
goto fail_inode;
+ /* reset this to 0 to cue lazy_getattr to give us a unique i_ino value
+ * if this ever has a getattr run against it */
+ inode->i_ino = 0;
+
pipe = alloc_pipe_info(inode);
if (!pipe)
goto fail_iput;
@@ -852,6 +860,7 @@ static struct inode * get_pipe_inode(voi
pipe->readers = pipe->writers = 1;
inode->i_fop = &rdwr_pipe_fops;
+ inode->i_op = &pipefs_inode_operations;
/*
* Mark the inode dirty from the very beginning,
@@ -998,7 +1007,12 @@ static int pipefs_get_sb(struct file_sys
int flags, const char *dev_name, void *data,
struct vfsmount *mnt)
{
- return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
+ static struct super_operations default_ops = {
+ .statfs = simple_statfs,
+ .drop_inode = generic_delete_inode,
+ };
+
+ return get_sb_pseudo(fs_type, "pipe:", &default_ops, PIPEFS_MAGIC, mnt);
}
static struct file_system_type pipe_fs_type = {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2fe6e3f..41571c1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1885,6 +1885,7 @@ extern int dcache_dir_close(struct inode
extern loff_t dcache_dir_lseek(struct file *, loff_t, int);
extern int dcache_readdir(struct file *, void *, filldir_t);
extern int simple_getattr(struct vfsmount *, struct dentry *, struct kstat *);
+extern int lazy_getattr(struct vfsmount *, struct dentry *, struct kstat *);
extern int simple_statfs(struct dentry *, struct kstatfs *);
extern int simple_link(struct dentry *, struct inode *, struct dentry *);
extern int simple_unlink(struct inode *, struct dentry *);
