Use f_bsize for ZFS afs_fsfragsize

On ZFS, the disk space files can use up can be rounded up to the next
recordsize boundary if they've been truncated. This can cause the Unix CM
to mis-estimate cache usage, since it truncates files fairly often, and
assumes the disk space used is the file length rounded up to the next
f_frsize.

Since the ZFS recordsize is available via the statvfs f_bsize, just
round up to that instead. There is still some additional file metadata
that takes up some additional space on disk, but according to ZFS people
I've spoken to about this, it cannot be known in advance. In practice,
the additional metadata storage doesn't appear to exceed about 10% of
the data storage, which should be acceptable.

FIXES 125365

Reviewed-on: http://gerrit.openafs.org/650
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Andrew Deason <adeason@sinenomine.net>

diff --git a/src/afs/afs_init.c b/src/afs/afs_init.c
index 2b1cae72ad3430b9303205ca33f655b27ffed3c9..b55ae7aa07618c9f79601d7f9a0a287987a071fb 100644 (file)
--- a/src/afs/afs_init.c
+++ b/src/afs/afs_init.c
@@ -425,7 +425,17 @@ afs_InitCacheInfo(register char *afile)
        if (!VFS_STATFS(filevp->v_vfsp, &st))
 #endif /* SGI... */
 #if    defined(AFS_SUN5_ENV) || defined(AFS_HPUX100_ENV)
-           afs_fsfragsize = st.f_frsize - 1;
+           if (strcmp("zfs", st.f_basetype) == 0) {
+               /*
+                * Files in ZFS can take up to around the next
+                * recordsize boundary after being truncated. recordsize
+                * is reported in statvfs by f_bsize, so use that
+                * instead.
+                */
+               afs_fsfragsize = st.f_bsize - 1;
+           } else {
+               afs_fsfragsize = st.f_frsize - 1;
+           }
 #else
            afs_fsfragsize = st.f_bsize - 1;
 #endif