ls internal API works faster than smb_stat

[Jeremy Allison]

On Tue, Feb 14, 2017 at 11:11:10PM +0530, shravan a wrote:
> Hi,
> 
> 
> LibSmbClient exposes an api  *int **smbc_opendir*(*const* *char* *durl) which
> accepts the parent folder path and fetches metadata about all its immediate
> children and returns the directory handle to the parent folder. The api
> *struct* smbc_dirent **smbc_readdir*(*unsigned* *int* dh) accepts this
> directory handle(dh) and returns metadata as a structure (smbc_dirent) that
> contains limited info such as smbc_type, dirlen, commentlen,comment,
> namelen, name. Repetitive calls to this API fetches the next child metadata
> in sequence and returns the structure. Unfortunately, it doesn’t give any
> information regarding the resource size(important in case of files),
> create/modified date time. To get these info, this library exposes two
> API’s,
> 
> *int* *smbc_stat*(*const* *char* *url, *struct* stat *st) - that accepts
> the url and
> 
> *int **smbc_fstat*(*int* fd, *struct* stat *st) that accepts the file
> descriptor.
> 
>      Both returns the required metadata as a structure ‘stat’ which
> contains all the time stamps(create, modified, access) and the size.  Both
> needs to be invoked once for every child resource within the parent
> resource. smbc_stat() is found to be an expensive task since it makes an
> extra SMB call to the resource , while smbc_fstat() is found to be faster
> since it accepts the file descriptor. But this still requires the file
> descriptor which can be obtained only via another smbc_opendir(resource
> url) or smbc_open(resource url).
> 
>   Another API I tried out is –
> 
> *Int **smbc_getxattr*(*const* *char* *fname,
> 
>               *const* *char* *name,
> 
>               *const* *void* *value,
> 
>               size_t size)
> 
>      This accepts the resourceurl, and the attribute name, returns the
> attribute value. But this API also needs to be invoked once per child
> resource within the parent folder which again is expensive.
> 
> 
> 
> This extra API call for every child resource still makes the whole process
> expensive.
> 
> 
> However, when I open a smb session from the shell "ls" command performs
> very fast. The function that "ls" internally calls in "list_dir".
> 
> I would like to write a public API that would call the internal
> implementation of "ls". Thoughts?

What you need is readdirplus - a readdir that also returns
stat info.

Add a new call to libsmbclient called smbc_readdirplus().

The internal call to cli_list gets most of the info you
want (except for the EA values) so you will need to change
the SMBC_opendir_ctx() function to use an internal callback
that does more with the info returned by cli_list.