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    SubjectRe: [PATCH 09/13] sysfs: Implement sysfs_getattr & sysfs_permission
    Quoting Eric W. Biederman (ebiederm@xmission.com):
    > From: Eric W. Biederman <ebiederm@xmission.com>
    >
    > With the implementation of sysfs_getattr and sysfs_permission
    > sysfs becomes able to lazily propogate inode attribute changes
    > from the sysfs_dirents to the vfs inodes. This paves the way
    > for deleting significant chunks of now unnecessary code.
    >
    > Acked-by: Tejun Heo <tj@kernel.org>
    > Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
    > ---
    > fs/sysfs/dir.c | 2 +
    > fs/sysfs/inode.c | 64 ++++++++++++++++++++++++++++++++++++++-------------
    > fs/sysfs/symlink.c | 3 ++
    > fs/sysfs/sysfs.h | 2 +
    > 4 files changed, 54 insertions(+), 17 deletions(-)
    >
    > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
    > index fa37126..25d052a 100644
    > --- a/fs/sysfs/dir.c
    > +++ b/fs/sysfs/dir.c
    > @@ -800,7 +800,9 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
    >
    > const struct inode_operations sysfs_dir_inode_operations = {
    > .lookup = sysfs_lookup,
    > + .permission = sysfs_permission,
    > .setattr = sysfs_setattr,
    > + .getattr = sysfs_getattr,
    > .setxattr = sysfs_setxattr,
    > };
    >
    > diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
    > index fccfb55..2dcafe8 100644
    > --- a/fs/sysfs/inode.c
    > +++ b/fs/sysfs/inode.c
    > @@ -37,7 +37,9 @@ static struct backing_dev_info sysfs_backing_dev_info = {
    > };
    >
    > static const struct inode_operations sysfs_inode_operations ={
    > + .permission = sysfs_permission,
    > .setattr = sysfs_setattr,
    > + .getattr = sysfs_getattr,
    > .setxattr = sysfs_setxattr,
    > };
    >
    > @@ -196,7 +198,6 @@ static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
    >
    > static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
    > {
    > - inode->i_mode = iattr->ia_mode;
    > inode->i_uid = iattr->ia_uid;
    > inode->i_gid = iattr->ia_gid;
    > inode->i_atime = iattr->ia_atime;
    > @@ -227,38 +228,56 @@ static int sysfs_count_nlink(struct sysfs_dirent *sd)
    > return nr + 2;
    > }
    >
    > +static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
    > +{
    > + struct sysfs_inode_attrs *iattrs = sd->s_iattr;
    > +
    > + inode->i_mode = sd->s_mode;
    > + if (iattrs) {
    > + /* sysfs_dirent has non-default attributes
    > + * get them from persistent copy in sysfs_dirent
    > + */
    > + set_inode_attr(inode, &iattrs->ia_iattr);
    > + security_inode_notifysecctx(inode,
    > + iattrs->ia_secdata,
    > + iattrs->ia_secdata_len);
    > + }
    > +
    > + if (sysfs_type(sd) == SYSFS_DIR)
    > + inode->i_nlink = sysfs_count_nlink(sd);
    > +}
    > +
    > +int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
    > +{
    > + struct sysfs_dirent *sd = dentry->d_fsdata;
    > + struct inode *inode = dentry->d_inode;
    > +
    > + mutex_lock(&sysfs_mutex);
    > + sysfs_refresh_inode(sd, inode);
    > + mutex_unlock(&sysfs_mutex);

    So the inode->i_mutex is not needed?

    > +
    > + generic_fillattr(inode, stat);
    > + return 0;
    > +}
    > +
    > static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
    > {
    > struct bin_attribute *bin_attr;
    > - struct sysfs_inode_attrs *iattrs;
    >
    > inode->i_private = sysfs_get(sd);
    > inode->i_mapping->a_ops = &sysfs_aops;
    > inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
    > inode->i_op = &sysfs_inode_operations;
    > - inode->i_ino = sd->s_ino;
    > lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
    >
    > - iattrs = sd->s_iattr;
    > - if (iattrs) {
    > - /* sysfs_dirent has non-default attributes
    > - * get them for the new inode from persistent copy
    > - * in sysfs_dirent
    > - */
    > - set_inode_attr(inode, &iattrs->ia_iattr);
    > - if (iattrs->ia_secdata)
    > - security_inode_notifysecctx(inode,
    > - iattrs->ia_secdata,
    > - iattrs->ia_secdata_len);
    > - } else
    > - set_default_inode_attr(inode, sd->s_mode);
    > + set_default_inode_attr(inode, sd->s_mode);
    > + sysfs_refresh_inode(sd, inode);
    >
    > /* initialize inode according to type */
    > switch (sysfs_type(sd)) {
    > case SYSFS_DIR:
    > inode->i_op = &sysfs_dir_inode_operations;
    > inode->i_fop = &sysfs_dir_operations;
    > - inode->i_nlink = sysfs_count_nlink(sd);
    > break;
    > case SYSFS_KOBJ_ATTR:
    > inode->i_size = PAGE_SIZE;
    > @@ -341,3 +360,14 @@ int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
    > else
    > return -ENOENT;
    > }
    > +
    > +int sysfs_permission(struct inode *inode, int mask)
    > +{
    > + struct sysfs_dirent *sd = inode->i_private;
    > +
    > + mutex_lock(&sysfs_mutex);
    > + sysfs_refresh_inode(sd, inode);
    > + mutex_unlock(&sysfs_mutex);
    > +
    > + return generic_permission(inode, mask, NULL);
    > +}
    > diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
    > index 1137418..c5eff49 100644
    > --- a/fs/sysfs/symlink.c
    > +++ b/fs/sysfs/symlink.c
    > @@ -214,6 +214,9 @@ const struct inode_operations sysfs_symlink_inode_operations = {
    > .readlink = generic_readlink,
    > .follow_link = sysfs_follow_link,
    > .put_link = sysfs_put_link,
    > + .setattr = sysfs_setattr,
    > + .getattr = sysfs_getattr,
    > + .permission = sysfs_permission,
    > };
    >
    >
    > diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
    > index a96d967..12ccc07 100644
    > --- a/fs/sysfs/sysfs.h
    > +++ b/fs/sysfs/sysfs.h
    > @@ -156,7 +156,9 @@ static inline void __sysfs_put(struct sysfs_dirent *sd)
    > struct inode *sysfs_get_inode(struct sysfs_dirent *sd);
    > void sysfs_delete_inode(struct inode *inode);
    > int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr *iattr);
    > +int sysfs_permission(struct inode *inode, int mask);
    > int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
    > +int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat);
    > int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
    > size_t size, int flags);
    > int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name);
    > --
    > 1.6.5.2.143.g8cc62
    >
    > --
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