[PVFS-developers] metadata file size checking

[Rob Ross]

Don,

I've applied your patch to CVS, but I'm thinking I might simplify this a
bit more before we're done.

Here's what I'm thinking: rather than having meta_creat() call meta_open()
at the end, just have it explicitly re-open on its own.  This will allow
us to avoid the extra write() of dummy data.

I've attached a patch.  Lemme know what you think.  Sorry that there is 
formatting junk in there that is distracting from the real purpose.

And thanks for the original patch!

Rob

On Thu, 6 May 2004, Porter Don wrote:

> I wanted to implement some protection against overwriting a metadata file
> that has not had the migration script run on it after an upgrade.  So I
> ended up stat-ing the file in meta-open and if it is not a directory and its
> size is not the same as a struct fmeta, then the manager will return an
> EINVAL (open to suggestions for better error code) and print a message to
> logs.  See below:
-------------- next part --------------
Index: mgr/meta/metaio.c
===================================================================
RCS file: /projects/cvsroot/pvfs/mgr/meta/metaio.c,v
retrieving revision 1.18
diff -r1.18 metaio.c
83c83,84
< 	if(0 > stat(pathname, &st)){
---
> 	if (stat(pathname, &st) < 0) 
> 	{
88,89c89,92
< 	if(S_ISREG(st.st_mode) && st.st_size != sizeof(struct fmeta)){
< 		fprintf(stderr, "Cowardly refusing to open %s because it is not the size I expect a metadata file to be.\n", pathname);
---
> 	if (S_ISREG(st.st_mode) && st.st_size != sizeof(struct fmeta))
> 	{
> 		fprintf(stderr, "Cowardly refusing to open %s because it is not the size I expect a metadata file to be.\n",
> 				  pathname);
108,110c111,112
< 	static struct fmeta fm;
< 	int fd, old_umask, cflags = O_RDWR | O_CREAT | O_EXCL,
< 	    mode = S_IRWXU | S_IRGRP | S_IROTH;
---
> 	int fd, old_umask, cflags = O_RDWR | O_CREAT | O_EXCL;
> 	int mode = S_IRWXU | S_IRGRP | S_IROTH;
116c118
< 	if(fd < 0){
---
> 	if (fd < 0) {
119,127d120
< 
< 	/* write in dummy fmeta so that meta_open will succeed.  This is ok
< 	 * because only md_open calls us directly and it will overwrite
< 	 * anyway
< 	 */
< 	if(sizeof(struct fmeta) != write(fd, &fm, sizeof(struct fmeta))){
< 		return(-1);
< 	}
< 
131c124,125
< 	return(meta_open(pathname, flags));
---
> 	flags &= ~O_CREAT;
> 	return(open(pathname, flags, 0));