RE: [PATCH v4 08/10] cifsd: add file operations

["Namjae Jeon" <namjae.jeon@samsung.com>]

> On Wed, Jun 02, 2021 at 12:48:45PM +0900, Namjae Jeon wrote:
> > +#include <linux/rwlock.h>
> > +
> > +#include "glob.h"
> > +#include "buffer_pool.h"
> > +#include "connection.h"
> > +#include "mgmt/ksmbd_ida.h"
> > +
> > +static struct kmem_cache *filp_cache;
> > +
> > +struct wm {
> > +	struct list_head	list;
> > +	unsigned int		sz;
> > +	char			buffer[0];
> 
> This should use buffer[];
Okay.

> 
> > +};
> > +
> > +struct wm_list {
> > +	struct list_head	list;
> > +	unsigned int		sz;
> > +
> > +	spinlock_t		wm_lock;
> > +	int			avail_wm;
> > +	struct list_head	idle_wm;
> > +	wait_queue_head_t	wm_wait;
> > +};
> 
> What does wm stand for?
> 
> This looks like arbitrary caching of vmalloc buffers.  I thought we decided to just make vmalloc suck
> less rather than papering over that?
Today I have checked that vmalloc performance improvement patch for big allocation is merged.
I will remove it on next version.

> 
> > +static LIST_HEAD(wm_lists);
> > +static DEFINE_RWLOCK(wm_lists_lock);
> 
> Especially as this isn't going to scale at all using global loists and locks.
Okay.

> 
> > +void ksmbd_free_file_struct(void *filp) {
> > +	kmem_cache_free(filp_cache, filp);
> > +}
> > +
> > +void *ksmbd_alloc_file_struct(void)
> > +{
> > +	return kmem_cache_zalloc(filp_cache, GFP_KERNEL); }
> 
> These are only ued in vfs_cache.c . So I'd suggest to just move filp_cache there and drop these
> wrappers.
Okay.

> 
> > +}
> > +
> > +static void ksmbd_vfs_inherit_owner(struct ksmbd_work *work,
> > +				    struct inode *parent_inode,
> > +				    struct inode *inode)
> > +{
> > +	if (!test_share_config_flag(work->tcon->share_conf,
> > +				    KSMBD_SHARE_FLAG_INHERIT_OWNER))
> > +		return;
> > +
> > +	i_uid_write(inode, i_uid_read(parent_inode)); }
> 
> Can you explain this a little more?  When do the normal create/mdir fail to inherit the owner?
The ownership of new files and directories is normally created with effective uid of the connected user.
There is "inherit owner" parameter(samba also have same one) to inherit the ownership of the parent directory.

> 
> int ksmbd_vfs_inode_permission(struct dentry *dentry, int acc_mode, bool delete)
> > +{
> > +	int mask, ret = 0;
> > +
> > +	mask = 0;
> > +	acc_mode &= O_ACCMODE;
> > +
> > +	if (acc_mode == O_RDONLY)
> > +		mask = MAY_READ;
> > +	else if (acc_mode == O_WRONLY)
> > +		mask = MAY_WRITE;
> > +	else if (acc_mode == O_RDWR)
> > +		mask = MAY_READ | MAY_WRITE;
> 
> How about already setting up the MAY_ flags in smb2_create_open_flags and returning them in extra
> argument?  That keeps the sm to Linux translation in a single place.
Right. Will update it.

> 
> > +
> > +	if (inode_permission(&init_user_ns, d_inode(dentry), mask | MAY_OPEN))
> > +		return -EACCES;
> 
> And this call can be open coded in the only caller.
Okay.

> 
> > +	if (delete) {
> 
> And this block could be split into a nice self-contained helper.
Okay.

> 
> > +		struct dentry *child, *parent;
> > +
> > +		parent = dget_parent(dentry);
> > +		inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
> > +		child = lookup_one_len(dentry->d_name.name, parent,
> > +				       dentry->d_name.len);
> > +		if (IS_ERR(child)) {
> > +			ret = PTR_ERR(child);
> > +			goto out_lock;
> > +		}
> > +
> > +		if (child != dentry) {
> > +			ret = -ESTALE;
> > +			dput(child);
> > +			goto out_lock;
> > +		}
> > +		dput(child);
> 
> That being said I do not understand the need for this re-lookup at all.
Al commented parent could be not stable, So checked staleness by re-lookup name under parent lock.

> 
> > +	if (!inode_permission(&init_user_ns, d_inode(dentry), MAY_OPEN |
> > +MAY_WRITE))
> 
> All these inode_permission lines have overly long lines.  It might be worth to pass the user_namespace
> to this function, not only to shorten the code, but also to prepare for user namespace support.
Okay, Let me check it.

> 
> > +	parent = dget_parent(dentry);
> > +	inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
> > +	child = lookup_one_len(dentry->d_name.name, parent,
> > +			       dentry->d_name.len);
> > +	if (IS_ERR(child)) {
> > +		ret = PTR_ERR(child);
> > +		goto out_lock;
> > +	}
> > +
> > +	if (child != dentry) {
> > +		ret = -ESTALE;
> > +		dput(child);
> > +		goto out_lock;
> > +	}
> > +	dput(child);
> 
> This is the same weird re-lookup dance as above.  IFF there is a good rationale for it it needs to go
> into a self-contained and well documented helper.
Okay.

> 
> > +int ksmbd_vfs_create(struct ksmbd_work *work, const char *name,
> > +umode_t mode) {
> > +	struct path path;
> > +	struct dentry *dentry;
> > +	int err;
> > +
> > +	dentry = kern_path_create(AT_FDCWD, name, &path, 0);
> 
> Curious:  why is this using absolute or CWD based path instead of doing lookups based off the parent
> as done by e.g. nfsd?  Same also for mkdir and co.
Because SMB create request is given an absolute path unlike NFS.

> 
> > +{
> > +	struct file *filp;
> > +	ssize_t nbytes = 0;
> > +	char *rbuf;
> > +	struct inode *inode;
> > +
> > +	rbuf = work->aux_payload_buf;
> > +	filp = fp->filp;
> > +	inode = file_inode(filp);
> 
> These can be initialized on the declaration lines to make the code a little easier to read.
Okay.

> 
> > +	if (!work->tcon->posix_extensions) {
> > +		spin_lock(&src_dent->d_lock);
> > +		list_for_each_entry(dst_dent, &src_dent->d_subdirs, d_child) {
> > +			struct ksmbd_file *child_fp;
> > +
> > +			if (d_really_is_negative(dst_dent))
> > +				continue;
> > +
> > +			child_fp = ksmbd_lookup_fd_inode(d_inode(dst_dent));
> > +			if (child_fp) {
> > +				spin_unlock(&src_dent->d_lock);
> > +				ksmbd_debug(VFS, "Forbid rename, sub file/dir is in use\n");
> > +				return -EACCES;
> > +			}
> > +		}
> > +		spin_unlock(&src_dent->d_lock);
> > +	}
> 
> This begs for being split into a self-contained helper.
Okay.

> 
> > +int ksmbd_vfs_lock(struct file *filp, int cmd, struct file_lock
> > +*flock) {
> > +	ksmbd_debug(VFS, "calling vfs_lock_file\n");
> > +	return vfs_lock_file(filp, cmd, flock, NULL); }
> > +
> > +int ksmbd_vfs_readdir(struct file *file, struct ksmbd_readdir_data
> > +*rdata) {
> > +	return iterate_dir(file, &rdata->ctx); }
> > +
> > +int ksmbd_vfs_alloc_size(struct ksmbd_work *work, struct ksmbd_file *fp,
> > +			 loff_t len)
> > +{
> > +	smb_break_all_levII_oplock(work, fp, 1);
> > +	return vfs_fallocate(fp->filp, FALLOC_FL_KEEP_SIZE, 0, len); }
> 
> Please avoid such trivial wrappers that just make the code hard to follow.
Okay.

> 
> > +int ksmbd_vfs_fqar_lseek(struct ksmbd_file *fp, loff_t start, loff_t length,
> > +			 struct file_allocated_range_buffer *ranges,
> > +			 int in_count, int *out_count)
> 
> What is fqar?
It is an abbreviation for FSCTL QUERY ALLOCATED RANGES.

> 
> > +
> > +/*
> > + * ksmbd_vfs_get_logical_sector_size() - get logical sector size from
> > +inode
> > + * @inode: inode
> > + *
> > + * Return: logical sector size
> > + */
> > +unsigned short ksmbd_vfs_logical_sector_size(struct inode *inode) {
> > +	struct request_queue *q;
> > +	unsigned short ret_val = 512;
> > +
> > +	if (!inode->i_sb->s_bdev)
> > +		return ret_val;
> > +
> > +	q = inode->i_sb->s_bdev->bd_disk->queue;
> > +
> > +	if (q && q->limits.logical_block_size)
> > +		ret_val = q->limits.logical_block_size;
> > +
> > +	return ret_val;
> 
> I don't think a CIFS server has any business poking into the block layer.  What is this trying to do?
Ah, Yes, We don't need do that. I will change it with statfs->f_bsize.

> 
> > +struct posix_acl *ksmbd_vfs_posix_acl_alloc(int count, gfp_t flags) {
> > +#if IS_ENABLED(CONFIG_FS_POSIX_ACL)
> > +	return posix_acl_alloc(count, flags); #else
> > +	return NULL;
> > +#endif
> > +}
> > +
> > +struct posix_acl *ksmbd_vfs_get_acl(struct inode *inode, int type) {
> > +#if IS_ENABLED(CONFIG_FS_POSIX_ACL)
> > +	return get_acl(inode, type);
> > +#else
> > +	return NULL;
> > +#endif
> > +}
> > +
> > +int ksmbd_vfs_set_posix_acl(struct inode *inode, int type,
> > +			    struct posix_acl *acl)
> > +{
> > +#if IS_ENABLED(CONFIG_FS_POSIX_ACL)
> > +	return set_posix_acl(&init_user_ns, inode, type, acl); #else
> > +	return -EOPNOTSUPP;
> > +#endif
> > +}
> 
> Please avoid these pointless wrappers and just use large code block ifdefs or IS_ENABLED checks.
Okay.

> 
> > +int ksmbd_vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> > +			      struct file *file_out, loff_t pos_out, size_t len) {
> > +	struct inode *inode_in = file_inode(file_in);
> > +	struct inode *inode_out = file_inode(file_out);
> > +	int ret;
> > +
> > +	ret = vfs_copy_file_range(file_in, pos_in, file_out, pos_out, len, 0);
> > +	/* do splice for the copy between different file systems */
> > +	if (ret != -EXDEV)
> > +		return ret;
> > +
> > +	if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
> > +		return -EISDIR;
> > +	if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
> > +		return -EINVAL;
> > +
> > +	if (!(file_in->f_mode & FMODE_READ) ||
> > +	    !(file_out->f_mode & FMODE_WRITE))
> > +		return -EBADF;
> > +
> > +	if (len == 0)
> > +		return 0;
> > +
> > +	file_start_write(file_out);
> > +
> > +	/*
> > +	 * skip the verification of the range of data. it will be done
> > +	 * in do_splice_direct
> > +	 */
> > +	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> > +			       len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> 
> vfs_copy_file_range already does this type of fallback, so this is dead code.
Okay.

> 
> > +#define XATTR_NAME_STREAM_LEN		(sizeof(XATTR_NAME_STREAM) - 1)
> > +
> > +enum {
> > +	XATTR_DOSINFO_ATTRIB		= 0x00000001,
> > +	XATTR_DOSINFO_EA_SIZE		= 0x00000002,
> > +	XATTR_DOSINFO_SIZE		= 0x00000004,
> > +	XATTR_DOSINFO_ALLOC_SIZE	= 0x00000008,
> > +	XATTR_DOSINFO_CREATE_TIME	= 0x00000010,
> > +	XATTR_DOSINFO_CHANGE_TIME	= 0x00000020,
> > +	XATTR_DOSINFO_ITIME		= 0x00000040
> > +};
> > +
> > +struct xattr_dos_attrib {
> > +	__u16	version;
> > +	__u32	flags;
> > +	__u32	attr;
> > +	__u32	ea_size;
> > +	__u64	size;
> > +	__u64	alloc_size;
> > +	__u64	create_time;
> > +	__u64	change_time;
> > +	__u64	itime;
> > +};
> 
> These looks like on-disk structures.  Any chance you could re-order the headers so that things like
> on-disk, on the wire and netlink uapi structures all have a dedicated and well documented header for
> themselves?
Okay.

> 
> > +	read_lock(&ci->m_lock);
> > +	list_for_each(cur, &ci->m_fp_list) {
> > +		lfp = list_entry(cur, struct ksmbd_file, node);
> 
> Please use list_for_each_entry.  There are very few places left where using list_for_each makes sense.
Okay.

> 
> > +		if (inode == FP_INODE(lfp)) {
> > +			atomic_dec(&ci->m_count);
> > +			read_unlock(&ci->m_lock);
> > +			return lfp;
> > +		}
> > +	}
> > +	atomic_dec(&ci->m_count);
> > +	read_unlock(&ci->m_lock);
> 
> So a successful find increments m_count, but a miss decreases it?
> Isn't this going to create an underflow?
m_count is increased from ksmbd_inode_lookup_by_vfsinode().
So m_count should be decreased regardless of finding it.

> 
> > +	if (!fp->f_ci) {
> > +		ksmbd_free_file_struct(fp);
> > +		return ERR_PTR(-ENOMEM);
> > +	}
> > +
> > +	ret = __open_id(&work->sess->file_table, fp, OPEN_ID_TYPE_VOLATILE_ID);
> > +	if (ret) {
> > +		ksmbd_inode_put(fp->f_ci);
> > +		ksmbd_free_file_struct(fp);
> > +		return ERR_PTR(ret);
> > +	}
> > +
> > +	atomic_inc(&work->conn->stats.open_files_count);
> > +	return fp;
> 
> Please use goto based unwinding instead of duplicating the resoure cleanup.
Okay.
> 
> > +static bool tree_conn_fd_check(struct ksmbd_tree_connect *tcon,
> > +struct ksmbd_file *fp)
> 
> Overly long line.
Recently, checkpatch.pl has been changed to allow up to 100 character.
You mean cut it to 80 character if possible?
> 
> > +{
> > +	return fp->tcon != tcon;
> > +}
> > +
> > +static bool session_fd_check(struct ksmbd_tree_connect *tcon, struct
> > +ksmbd_file *fp)
> 
> Same.
Okay.