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Commit 630458e7 authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

nfsd4: factor ctime into change attribute 



Factoring ctime into the nfsv4 change attribute gives us better
properties than just i_version alone.

Eventually we'll likely also expose this (as opposed to raw i_version)
to userspace, at which point we'll want to move it to a common helper,
called from either userspace or individual filesystems.  For now, nfsd
is the only user.

Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 35a30fc3

fs/nfsd/nfs3xdr.c

+1 −1
Original line number Diff line number Diff line
@@ -260,7 +260,7 @@ void fill_post_wcc(struct svc_fh *fhp) 
		printk("nfsd: inode locked twice during operation.\n");



	err = fh_getattr(fhp, &fhp->fh_post_attr);

	fhp->fh_post_change = d_inode(fhp->fh_dentry)->i_version;

	fhp->fh_post_change = nfsd4_change_attribute(d_inode(fhp->fh_dentry));

	if (err) {

		fhp->fh_post_saved = false;

		/* Grab the ctime anyway - set_change_info might use it */

fs/nfsd/nfs4xdr.c

+1 −1
Original line number Diff line number Diff line
@@ -1973,7 +1973,7 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode, 
		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));

		*p++ = 0;

	} else if (IS_I_VERSION(inode)) {

		p = xdr_encode_hyper(p, inode->i_version);

		p = xdr_encode_hyper(p, nfsd4_change_attribute(inode));

	} else {

		*p++ = cpu_to_be32(stat->ctime.tv_sec);

		*p++ = cpu_to_be32(stat->ctime.tv_nsec);

fs/nfsd/nfsfh.h

+23 −1
Original line number Diff line number Diff line
@@ -240,6 +240,28 @@ fh_clear_wcc(struct svc_fh *fhp) 
	fhp->fh_pre_saved = false;

}



/*

 * We could use i_version alone as the change attribute.  However,

 * i_version can go backwards after a reboot.  On its own that doesn't

 * necessarily cause a problem, but if i_version goes backwards and then

 * is incremented again it could reuse a value that was previously used

 * before boot, and a client who queried the two values might

 * incorrectly assume nothing changed.

 *

 * By using both ctime and the i_version counter we guarantee that as

 * long as time doesn't go backwards we never reuse an old value.

 */

static inline u64 nfsd4_change_attribute(struct inode *inode)

{

	u64 chattr;



	chattr =  inode->i_ctime.tv_sec;

	chattr <<= 30;

	chattr += inode->i_ctime.tv_nsec;

	chattr += inode->i_version;

	return chattr;

}



/*

 * Fill in the pre_op attr for the wcc data

 */
@@ -253,7 +275,7 @@ fill_pre_wcc(struct svc_fh *fhp) 
		fhp->fh_pre_mtime = inode->i_mtime;

		fhp->fh_pre_ctime = inode->i_ctime;

		fhp->fh_pre_size  = inode->i_size;

		fhp->fh_pre_change = inode->i_version;

		fhp->fh_pre_change = nfsd4_change_attribute(inode);

		fhp->fh_pre_saved = true;

	}

}