Date: Sun, 21 May 2017 16:03:55 +0200 From: Jilles Tjoelker <jilles@stack.nl> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-current@freebsd.org, freebsd-fs@freebsd.org, freebsd-ports@freebsd.org, emaste@freebsd.org, Kirk McKusick <mckusick@mckusick.com> Subject: Re: 64-bit inodes (ino64) Status Update and Call for Testing Message-ID: <20170521140355.GC21613@stack.nl> In-Reply-To: <20170521123118.GH1622@kib.kiev.ua> References: <20170420194314.GI1788@kib.kiev.ua> <20170521121456.GA21613@stack.nl> <20170521123118.GH1622@kib.kiev.ua>
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On Sun, May 21, 2017 at 03:31:18PM +0300, Konstantin Belousov wrote: > On Sun, May 21, 2017 at 02:14:56PM +0200, Jilles Tjoelker wrote: > > We have another type in this area which is too small in some situations: > > uint8_t for struct dirent.d_namlen. For filesystems that store filenames > > as upto 255 UTF-16 code units, the name to be stored in d_name may be > > upto 765 bytes long in UTF-8. This was reported in PR 204643. The code > > currently handles this by returning the short (8.3) name, but this name > > may not be present or usable, leaving the file inaccessible. > > Actually allowing longer names seems too complicated to add to the ino64 > > change, but changing d_namlen to uint16_t (using d_pad0 space) and > > skipping entries with d_namlen > 255 in libc may be helpful. > > Note that applications using the deprecated readdir_r() will not be able > > to read such long names, since the API does not allow specifying that a > > larger buffer has been provided. (This could be avoided by making struct > > dirent.d_name 766 bytes long instead of 256.) > > Unfortunately, the existence of readdir_r() also prevents changing > > struct dirent.d_name to the more correct flexible array. > Yes, changing the size of d_name at this stage of the project is out of > question. My reading of your proposal is that we should extend the size > of d_namlen to uint16_t, am I right ? Should we go to 32bit directly > then, perhaps ? Yes, my proposal is to change d_namlen to uint16_t. Making it 32 bits is not useful with the 16-bit d_reclen, and increasing d_reclen does not seem useful to me with the current model of getdirentries() where the whole dirent must fit into the caller's buffer. > I did not committed the change below, nor did I tested or even build it. I'd like to skip overlong names in the native readdir_r() as well, so that long name support can be added to the kernel later without causing buffer overflows with applications using FreeBSD 12.0 libc. The native readdir() does not seem to have such a problem. > [patch snipped] -- Jilles Tjoelker
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