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Allow FreeBSD mount NetBSD's FFSv2 WAPBL read-only #2279

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Allow FreeBSD mount NetBSD's FFSv2 WAPBL read-only #2279

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14 changes: 13 additions & 1 deletion sys/ufs/ffs/ffs_subr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -717,7 +717,19 @@
howmany(fs->fs_cssize, fs->fs_fsize), %jd);
#endif
WCHK(fs->fs_metaspace, <, 0, %jd);
WCHK(fs->fs_metaspace, >, fs->fs_fpg / 2, %jd);
/*
* FreeBSD and NetBSD FFSv2 layouts diverge in the superblock region
* following fs_maxbsize. NetBSD's WAPBL journal metadata occupies
* the same bytes as FreeBSD's fs_metaspace and other fields.
* fs_flags cannot serve as a discriminator: ffs_oldfscompat_read()
* may overwrite it from the 8-bit fs_old_flags before this check runs.
* Skip the upper-bound check for UFS2; ffs_mountfs() detects the
* condition and enforces read-only access without modifying the
* on-disk superblock. The check is preserved for UFS1 where no such
* layout divergence exists.
*/
if (fs->fs_magic != FS_UFS2_MAGIC)
WCHK(fs->fs_metaspace, >, fs->fs_fpg / 2, %jd);

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WCHK(fs->fs_minfree, >, 99, %jd%%);
maxfilesize = fs->fs_bsize * UFS_NDADDR - 1;
for (sizepb = fs->fs_bsize, i = 0; i < UFS_NIADDR; i++) {
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27 changes: 27 additions & 0 deletions sys/ufs/ffs/ffs_vfsops.c
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Original file line number Diff line number Diff line change
Expand Up @@ -604,6 +604,16 @@ ffs_mount(struct mount *mp)
if (error) {
return (error);
}
/*
* Refuse upgrade of NetBSD WAPBL filesystem to
* read-write; see validate_sblock() for details.
*/
if (fs->fs_magic == FS_UFS2_MAGIC &&
fs->fs_metaspace > fs->fs_fpg / 2) {
vfs_mount_error(mp, "NetBSD WAPBL filesystem "
"must be mounted read-only");
return (EROFS);
}
fs->fs_flags &= ~FS_UNCLEAN;
if (fs->fs_clean == 0) {
fs->fs_flags |= FS_UNCLEAN;
Expand Down Expand Up @@ -926,6 +936,23 @@ ffs_mountfs(struct vnode *odevvp, struct mount *mp, struct thread *td)
ffs_use_bread);
if (error != 0)
goto out;
/*
* Per NetBSD's wapbl(4), systems without WAPBL support should mount it
* read-only; see validate_sblock() for details.
*/
if (fs->fs_magic == FS_UFS2_MAGIC &&
fs->fs_metaspace > fs->fs_fpg / 2) {
if ((mp->mnt_flag & MNT_RDONLY) == 0) {
vfs_mount_error(mp, "NetBSD WAPBL filesystem must be "
"mounted read-only");
error = EROFS;
goto out;
}
printf("WARNING: %s: NetBSD WAPBL filesystem mounted "
"read-only (fs_metaspace %jd, fs_fpg/2 %jd)\n",
mp->mnt_stat.f_mntonname, (intmax_t)fs->fs_metaspace,
(intmax_t)fs->fs_fpg / 2);
}
fs->fs_flags &= ~FS_UNCLEAN;
if (fs->fs_clean == 0) {
fs->fs_flags |= FS_UNCLEAN;
Expand Down
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