vfs: default to generic_readlink()
If i_op->readlink is NULL, but i_op->get_link is set then vfs_readlink() defaults to calling generic_readlink(). The IOP_DEFAULT_READLINK flag indicates that the above conditions are met and the default action can be taken. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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@ -596,3 +596,7 @@ in your dentry operations instead.
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[mandatory]
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[mandatory]
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->rename() has an added flags argument. Any flags not handled by the
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->rename() has an added flags argument. Any flags not handled by the
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filesystem should result in EINVAL being returned.
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filesystem should result in EINVAL being returned.
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--
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[recommended]
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->readlink is optional for symlinks. Don't set, unless filesystem needs
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to fake something for readlink(2).
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@ -451,9 +451,6 @@ otherwise noted.
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exist; this is checked by the VFS. Unlike plain rename,
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exist; this is checked by the VFS. Unlike plain rename,
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source and target may be of different type.
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source and target may be of different type.
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readlink: called by the readlink(2) system call. Only required if
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you want to support reading symbolic links
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get_link: called by the VFS to follow a symbolic link to the
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get_link: called by the VFS to follow a symbolic link to the
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inode it points to. Only required if you want to support
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inode it points to. Only required if you want to support
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symbolic links. This method returns the symlink body
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symbolic links. This method returns the symlink body
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@ -468,6 +465,12 @@ otherwise noted.
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argument. If request can't be handled without leaving RCU mode,
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argument. If request can't be handled without leaving RCU mode,
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have it return ERR_PTR(-ECHILD).
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have it return ERR_PTR(-ECHILD).
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readlink: this is now just an override for use by readlink(2) for the
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cases when ->get_link uses nd_jump_link() or object is not in
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fact a symlink. Normally filesystems should only implement
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->get_link for symlinks and readlink(2) will automatically use
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that.
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permission: called by the VFS to check for access rights on a POSIX-like
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permission: called by the VFS to check for access rights on a POSIX-like
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filesystem.
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filesystem.
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15
fs/namei.c
15
fs/namei.c
@ -4682,10 +4682,19 @@ int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
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{
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{
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struct inode *inode = d_inode(dentry);
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struct inode *inode = d_inode(dentry);
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if (!inode->i_op->readlink)
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if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
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return -EINVAL;
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if (unlikely(inode->i_op->readlink))
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return inode->i_op->readlink(dentry, buffer, buflen);
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return inode->i_op->readlink(dentry, buffer, buflen);
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if (!d_is_symlink(dentry))
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return -EINVAL;
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spin_lock(&inode->i_lock);
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inode->i_opflags |= IOP_DEFAULT_READLINK;
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spin_unlock(&inode->i_lock);
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}
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return generic_readlink(dentry, buffer, buflen);
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}
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}
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EXPORT_SYMBOL(vfs_readlink);
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EXPORT_SYMBOL(vfs_readlink);
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@ -595,6 +595,7 @@ is_uncached_acl(struct posix_acl *acl)
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#define IOP_LOOKUP 0x0002
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#define IOP_LOOKUP 0x0002
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#define IOP_NOFOLLOW 0x0004
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#define IOP_NOFOLLOW 0x0004
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#define IOP_XATTR 0x0008
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#define IOP_XATTR 0x0008
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#define IOP_DEFAULT_READLINK 0x0010
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/*
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/*
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* Keep mostly read-only and often accessed (especially for
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* Keep mostly read-only and often accessed (especially for
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