Re: Max. number of subdirectories dump

[Johnny Billquist <bqt%softjar.se@localhost>]

On 2013-08-18 17:50, Johnny Billquist wrote:
> On 2013-08-18 17:38, Joerg Sonnenberger wrote:
> > On Sun, Aug 18, 2013 at 05:36:47PM +0200, Johnny Billquist wrote:
> > > There is nothing in the directory entry that even tells if the entry
> > > is a directory or just a plain file, unless I remember wrong. And
> > > they are not sorted so that all directories comes first...
> >
> > There is a type tag for each directory entry.
>
> That's what I get for just trying to remember instead of actually
> checking. :-)

By the way. Sorry for spinning a little offtopic right now.
Looking at 2.11BSD, it looks like this:

struct  direct {
        ino_t   d_ino;                  /* inode number of entry */
        u_short d_reclen;               /* length of this record */
        u_short d_namlen;               /* length of string in d_name */
        char    d_name[MAXNAMLEN+1];    /* name must be no longer than 
this */
};

(MAXNAMLEN is 63 for 2.11BSD, by the way...)

In NetBSD (fairly current):

struct dirent {
        ino_t d_fileno;                 /* file number of entry */
        uint16_t d_reclen;              /* length of this record */
        uint16_t d_namlen;              /* length of string in d_name */
        uint8_t  d_type;                /* file type, see below */
#if defined(_NETBSD_SOURCE)
#define MAXNAMLEN       511             /* must be kept in sync with 
NAME_MAX */
        char    d_name[MAXNAMLEN + 1];  /* name must be no longer than 
this */
#else
        char    d_name[511 + 1];        /* name must be no longer than 
this */
#endif
};


So obviously I'm only (as always) just a few years behind... :-D

It's an obvious optimization to keep type already in the directory 
itself. But is there any other reason why it was added there? It 
obviously means you have the same information in two places, with all 
the obvious risks of having the data out of sync, and potential mess 
from that... (I'm assuming the information is still in the inode anyway, 
since it could be interesting with hard links otherwise. By the way, 
this would assume that hard links must check what kind of thing you are 
adding a link to, so that your new directory entry gets the right type?)

        Johnny

--
Johnny Billquist                  || "I'm on a bus
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