RE: stupid FS questions
On Tue, 30 May 2000, Garrett Wollman wrote: On Tue, 30 May 2000 16:20:53 -0400, "Yevmenkin, Maksim N, CSCIO" [EMAIL PROTECTED] said: i know that :) i guess my questions were 1) why the same piece of code duplicated in all ``mount_xxx'' utilities? Because the original loadable module system held strongly to the religion that the kernel should never load anything of its own accord. The designers of the current loadable module system made different design choices, but the some traces of its predecessor still remain. Including defunct traces like all the duplicated code in the mount utilities :-). Relevant history: RCS file: /home/ncvs/src/lib/libc/gen/getvfsent.c,v Working file: getvfsent.c head: 1.14 revision 1.13 date: 1998/11/03 15:02:29; author: peter; state: Exp; lines: +10 -1 A feeble attempt at kld compatability. The mount_* programs assume that they cannot mount a filesystem that they cannot see in getvfsbyname(). Part 1 of this is a hack, make vfsisloadable() always return true - the ultimate decider of whether it's loadable or not is kldload() or mount(). Part 2 of this is to have vfsload() call kldload(2) and return success if it works. This means that we will use a viable kld module in preference to an LKM! Ultimately, the thing to do is remove the hacks to do a vfsload in all the ^^ should have been more than a year ago mount_* commands and let the kernel do it by itself in mount(2). RCS file: /home/ncvs/src/sys/kern/vfs_syscalls.c,v Working file: vfs_syscalls.c head: 1.153 ... revision 1.110 date: 1998/11/03 14:29:09; author: peter; state: Exp; lines: +32 -3 make mount(2) automatically kldload modules if the requested filesystem isn't present. This commit made the duplicated code redundant except for backwards compatibility. Bruce To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: stupid FS questions
I believe that it is used to dynamic load filesystem modules. Please read
the following pages to understand what is a kernel module:
http://thc.inferno.tusculum.edu/files/thc/bsdkern.html
-Zhihui
On Tue, 30 May 2000, Yevmenkin, Maksim N, CSCIO wrote:
Hello All,
i've been looking at ``mount_xxx'' code and have noticed "strange" thing.
all ``mount_xxx'' utilities have common part of code, like
error = getvfsbyname("xxx", vfc);
if (error vfsisloadable("xxx")) {
if (vfsload("xxx"))
err(EX_OSERR, "vfsload(xxx)");
endvfsent();/* flush cache */
error = getvfsbyname("xxx", vfc);
}
if (error)
errx(1, "xxx filesystem is not available");
if (mount(vfc.vfc_name, dir, mntflags, args) 0)
err(1, NULL);
1) what is the reason for this? why can't move this code to ``mount''?
2) what is the purpose of the following code in
``/sys/kern/vfs_syscalls.c''?
...
for (vfsp = vfsconf; vfsp; vfsp = vfsp-vfc_next)
if (!strcmp(vfsp-vfc_name, fstypename))
break;
if (vfsp == NULL) {
linker_file_t lf;
/* Refuse to load modules if securelevel raised */
if (securelevel 0) {
vput(vp);
return EPERM;
}
/* Only load modules for root (very important!) */
if ((error = suser(p)) != 0) {
vput(vp);
return error;
}
error = linker_load_file(fstypename, lf);
if (error || lf == NULL) {
vput(vp);
if (lf == NULL)
error = ENODEV;
return error;
}
...
from my understanding this is done to load FS module.
or did i miss someting?
thanks,
emax
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To Unsubscribe: send mail to [EMAIL PROTECTED]
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RE: stupid FS questions
i know that :) i guess my questions were
1) why the same piece of code duplicated in all ``mount_xxx'' utilities?
2) if we are loading fs kernel module from ``mount_xxx'' why
we have to do it again in kernel?
if i'm not missing anything, by the time we reach ``mount''
function, fs module will be in the memory and this code will
never be executed.
thanks,
emax
I believe that it is used to dynamic load filesystem modules.
Please read
the following pages to understand what is a kernel module:
http://thc.inferno.tusculum.edu/files/thc/bsdkern.html
i've been looking at ``mount_xxx'' code and have noticed
"strange" thing.
all ``mount_xxx'' utilities have common part of code, like
error = getvfsbyname("xxx", vfc);
if (error vfsisloadable("xxx")) {
if (vfsload("xxx"))
err(EX_OSERR, "vfsload(xxx)");
endvfsent();/* flush cache */
error = getvfsbyname("xxx", vfc);
}
if (error)
errx(1, "xxx filesystem is not available");
if (mount(vfc.vfc_name, dir, mntflags, args) 0)
err(1, NULL);
1) what is the reason for this? why can't move this code to
``mount''?
2) what is the purpose of the following code in
``/sys/kern/vfs_syscalls.c''?
...
for (vfsp = vfsconf; vfsp; vfsp = vfsp-vfc_next)
if (!strcmp(vfsp-vfc_name, fstypename))
break;
if (vfsp == NULL) {
linker_file_t lf;
/* Refuse to load modules if securelevel raised */
if (securelevel 0) {
vput(vp);
return EPERM;
}
/* Only load modules for root (very important!) */
if ((error = suser(p)) != 0) {
vput(vp);
return error;
}
error = linker_load_file(fstypename, lf);
if (error || lf == NULL) {
vput(vp);
if (lf == NULL)
error = ENODEV;
return error;
}
...
from my understanding this is done to load FS module.
or did i miss someting?
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-current" in the body of the message
RE: stupid FS questions
On Tue, 30 May 2000 16:20:53 -0400, "Yevmenkin, Maksim N, CSCIO" [EMAIL PROTECTED] said: i know that :) i guess my questions were 1) why the same piece of code duplicated in all ``mount_xxx'' utilities? Because the original loadable module system held strongly to the religion that the kernel should never load anything of its own accord. The designers of the current loadable module system made different design choices, but the some traces of its predecessor still remain. -GAWollman -- Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same [EMAIL PROTECTED] | O Siem / The fires of freedom Opinions not those of| Dance in the burning flame MIT, LCS, CRS, or NSA| - Susan Aglukark and Chad Irschick To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: stupid FS questions
On Tue, 30 May 2000, Zhihui Zhang wrote: http://thc.inferno.tusculum.edu/files/thc/bsdkern.html That stuff is excellent. It belongs in doc/. Any chances of it making it there? Brandon D. Valentine -- "You should believe in death, taxes, Larry Ellison's loathing of Bill Gates and Intel's inability to ship a working chipset." - Dr Spinola, The Register, 05/13/2000 To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
