diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.rst similarity index 99% rename from Documentation/filesystems/overlayfs.txt rename to Documentation/filesystems/overlayfs.rst index 845d689e0fd7..e443be7928db 100644 --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.rst @@ -1,3 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + Written by: Neil Brown Please see MAINTAINERS file for where to send questions. @@ -181,7 +183,7 @@ Kernel config options: worried about backward compatibility with kernels that have the redirect_dir feature and follow redirects even if turned off. -Module options (can also be changed through /sys/module/overlay/parameters/*): +Module options (can also be changed through /sys/module/overlay/parameters/): - "redirect_dir=BOOL": See OVERLAY_FS_REDIRECT_DIR kernel config option above. @@ -263,7 +265,7 @@ top, lower2 the middle and lower3 the bottom layer. Metadata only copy up --------------------- +--------------------- When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation @@ -286,10 +288,10 @@ pointed by REDIRECT. This should not be possible on local system as setting "trusted." xattrs will require CAP_SYS_ADMIN. But it should be possible for untrusted layers like from a pen drive. -Note: redirect_dir={off|nofollow|follow(*)} conflicts with metacopy=on, and +Note: redirect_dir={off|nofollow|follow[*]} conflicts with metacopy=on, and results in an error. -(*) redirect_dir=follow only conflicts with metacopy=on if upperdir=... is +[*] redirect_dir=follow only conflicts with metacopy=on if upperdir=... is given. Sharing and copying layers diff --git a/MAINTAINERS b/MAINTAINERS index b540ecc4e2a3..cc0a4a8ae06a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -12394,7 +12394,7 @@ L: linux-unionfs@vger.kernel.org T: git git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git S: Supported F: fs/overlayfs/ -F: Documentation/filesystems/overlayfs.txt +F: Documentation/filesystems/overlayfs.rst P54 WIRELESS DRIVER M: Christian Lamparter diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index b801c6353100..6220642fe113 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -227,13 +227,17 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper) { struct ovl_fh *fh; - int fh_type, fh_len, dwords; - void *buf; + int fh_type, dwords; int buflen = MAX_HANDLE_SZ; uuid_t *uuid = &real->d_sb->s_uuid; + int err; - buf = kmalloc(buflen, GFP_KERNEL); - if (!buf) + /* Make sure the real fid stays 32bit aligned */ + BUILD_BUG_ON(OVL_FH_FID_OFFSET % 4); + BUILD_BUG_ON(MAX_HANDLE_SZ + OVL_FH_FID_OFFSET > 255); + + fh = kzalloc(buflen + OVL_FH_FID_OFFSET, GFP_KERNEL); + if (!fh) return ERR_PTR(-ENOMEM); /* @@ -242,27 +246,19 @@ struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper) * the price or reconnecting the dentry. */ dwords = buflen >> 2; - fh_type = exportfs_encode_fh(real, buf, &dwords, 0); + fh_type = exportfs_encode_fh(real, (void *)fh->fb.fid, &dwords, 0); buflen = (dwords << 2); - fh = ERR_PTR(-EIO); + err = -EIO; if (WARN_ON(fh_type < 0) || WARN_ON(buflen > MAX_HANDLE_SZ) || WARN_ON(fh_type == FILEID_INVALID)) - goto out; + goto out_err; - BUILD_BUG_ON(MAX_HANDLE_SZ + offsetof(struct ovl_fh, fid) > 255); - fh_len = offsetof(struct ovl_fh, fid) + buflen; - fh = kmalloc(fh_len, GFP_KERNEL); - if (!fh) { - fh = ERR_PTR(-ENOMEM); - goto out; - } - - fh->version = OVL_FH_VERSION; - fh->magic = OVL_FH_MAGIC; - fh->type = fh_type; - fh->flags = OVL_FH_FLAG_CPU_ENDIAN; + fh->fb.version = OVL_FH_VERSION; + fh->fb.magic = OVL_FH_MAGIC; + fh->fb.type = fh_type; + fh->fb.flags = OVL_FH_FLAG_CPU_ENDIAN; /* * When we will want to decode an overlay dentry from this handle * and all layers are on the same fs, if we get a disconncted real @@ -270,14 +266,15 @@ struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper) * it to upperdentry or to lowerstack is by checking this flag. */ if (is_upper) - fh->flags |= OVL_FH_FLAG_PATH_UPPER; - fh->len = fh_len; - fh->uuid = *uuid; - memcpy(fh->fid, buf, buflen); + fh->fb.flags |= OVL_FH_FLAG_PATH_UPPER; + fh->fb.len = sizeof(fh->fb) + buflen; + fh->fb.uuid = *uuid; -out: - kfree(buf); return fh; + +out_err: + kfree(fh); + return ERR_PTR(err); } int ovl_set_origin(struct dentry *dentry, struct dentry *lower, @@ -300,8 +297,8 @@ int ovl_set_origin(struct dentry *dentry, struct dentry *lower, /* * Do not fail when upper doesn't support xattrs. */ - err = ovl_check_setxattr(dentry, upper, OVL_XATTR_ORIGIN, fh, - fh ? fh->len : 0, 0); + err = ovl_check_setxattr(dentry, upper, OVL_XATTR_ORIGIN, fh->buf, + fh ? fh->fb.len : 0, 0); kfree(fh); return err; @@ -317,7 +314,7 @@ static int ovl_set_upper_fh(struct dentry *upper, struct dentry *index) if (IS_ERR(fh)) return PTR_ERR(fh); - err = ovl_do_setxattr(index, OVL_XATTR_UPPER, fh, fh->len, 0); + err = ovl_do_setxattr(index, OVL_XATTR_UPPER, fh->buf, fh->fb.len, 0); kfree(fh); return err; diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index 702aa63f6774..29abdb1d3b5c 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -1170,7 +1170,7 @@ static int ovl_rename(struct inode *olddir, struct dentry *old, if (newdentry == trap) goto out_dput; - if (WARN_ON(olddentry->d_inode == newdentry->d_inode)) + if (olddentry->d_inode == newdentry->d_inode) goto out_dput; err = 0; diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 73c9775215b3..70e55588aedc 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -211,10 +211,11 @@ static int ovl_check_encode_origin(struct dentry *dentry) return 1; } -static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen) +static int ovl_dentry_to_fid(struct dentry *dentry, u32 *fid, int buflen) { struct ovl_fh *fh = NULL; int err, enc_lower; + int len; /* * Check if we should encode a lower or upper file handle and maybe @@ -231,11 +232,12 @@ static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen) return PTR_ERR(fh); err = -EOVERFLOW; - if (fh->len > buflen) + len = OVL_FH_LEN(fh); + if (len > buflen) goto fail; - memcpy(buf, (char *)fh, fh->len); - err = fh->len; + memcpy(fid, fh, len); + err = len; out: kfree(fh); @@ -243,31 +245,16 @@ out: fail: pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n", - dentry, err, buflen, fh ? (int)fh->len : 0, - fh ? fh->type : 0); + dentry, err, buflen, fh ? (int)fh->fb.len : 0, + fh ? fh->fb.type : 0); goto out; } -static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len) -{ - int res, len = *max_len << 2; - - res = ovl_d_to_fh(dentry, (char *)fid, len); - if (res <= 0) - return FILEID_INVALID; - - len = res; - - /* Round up to dwords */ - *max_len = (len + 3) >> 2; - return OVL_FILEID; -} - static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len, struct inode *parent) { struct dentry *dentry; - int type; + int bytes = *max_len << 2; /* TODO: encode connectable file handles */ if (parent) @@ -277,10 +264,14 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len, if (WARN_ON(!dentry)) return FILEID_INVALID; - type = ovl_dentry_to_fh(dentry, fid, max_len); - + bytes = ovl_dentry_to_fid(dentry, fid, bytes); dput(dentry); - return type; + if (bytes <= 0) + return FILEID_INVALID; + + *max_len = bytes >> 2; + + return OVL_FILEID_V1; } /* @@ -777,24 +768,45 @@ out_err: goto out; } +static struct ovl_fh *ovl_fid_to_fh(struct fid *fid, int buflen, int fh_type) +{ + struct ovl_fh *fh; + + /* If on-wire inner fid is aligned - nothing to do */ + if (fh_type == OVL_FILEID_V1) + return (struct ovl_fh *)fid; + + if (fh_type != OVL_FILEID_V0) + return ERR_PTR(-EINVAL); + + fh = kzalloc(buflen, GFP_KERNEL); + if (!fh) + return ERR_PTR(-ENOMEM); + + /* Copy unaligned inner fh into aligned buffer */ + memcpy(&fh->fb, fid, buflen - OVL_FH_WIRE_OFFSET); + return fh; +} + static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len, int fh_type) { struct dentry *dentry = NULL; - struct ovl_fh *fh = (struct ovl_fh *) fid; + struct ovl_fh *fh = NULL; int len = fh_len << 2; unsigned int flags = 0; int err; - err = -EINVAL; - if (fh_type != OVL_FILEID) + fh = ovl_fid_to_fh(fid, len, fh_type); + err = PTR_ERR(fh); + if (IS_ERR(fh)) goto out_err; err = ovl_check_fh_len(fh, len); if (err) goto out_err; - flags = fh->flags; + flags = fh->fb.flags; dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ? ovl_upper_fh_to_d(sb, fh) : ovl_lower_fh_to_d(sb, fh); @@ -802,12 +814,18 @@ static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, if (IS_ERR(dentry) && err != -ESTALE) goto out_err; +out: + /* We may have needed to re-align OVL_FILEID_V0 */ + if (!IS_ERR_OR_NULL(fh) && fh != (void *)fid) + kfree(fh); + return dentry; out_err: pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n", - len, fh_type, flags, err); - return ERR_PTR(err); + fh_len, fh_type, flags, err); + dentry = ERR_PTR(err); + goto out; } static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid, diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index bc14781886bf..b045cf1826fc 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -200,8 +200,14 @@ int ovl_getattr(const struct path *path, struct kstat *stat, if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) || (!ovl_verify_lower(dentry->d_sb) && (is_dir || lowerstat.nlink == 1))) { - stat->ino = lowerstat.ino; lower_layer = ovl_layer_lower(dentry); + /* + * Cannot use origin st_dev;st_ino because + * origin inode content may differ from overlay + * inode content. + */ + if (samefs || lower_layer->fsid) + stat->ino = lowerstat.ino; } /* diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index c269d6033525..76ff66339173 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -84,21 +84,21 @@ static int ovl_acceptable(void *ctx, struct dentry *dentry) * Return -ENODATA for "origin unknown". * Return <0 for an invalid file handle. */ -int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) +int ovl_check_fb_len(struct ovl_fb *fb, int fb_len) { - if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len) + if (fb_len < sizeof(struct ovl_fb) || fb_len < fb->len) return -EINVAL; - if (fh->magic != OVL_FH_MAGIC) + if (fb->magic != OVL_FH_MAGIC) return -EINVAL; /* Treat larger version and unknown flags as "origin unknown" */ - if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL) + if (fb->version > OVL_FH_VERSION || fb->flags & ~OVL_FH_FLAG_ALL) return -ENODATA; /* Treat endianness mismatch as "origin unknown" */ - if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) && - (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN) + if (!(fb->flags & OVL_FH_FLAG_ANY_ENDIAN) && + (fb->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN) return -ENODATA; return 0; @@ -119,15 +119,15 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name) if (res == 0) return NULL; - fh = kzalloc(res, GFP_KERNEL); + fh = kzalloc(res + OVL_FH_WIRE_OFFSET, GFP_KERNEL); if (!fh) return ERR_PTR(-ENOMEM); - res = vfs_getxattr(dentry, name, fh, res); + res = vfs_getxattr(dentry, name, fh->buf, res); if (res < 0) goto fail; - err = ovl_check_fh_len(fh, res); + err = ovl_check_fb_len(&fh->fb, res); if (err < 0) { if (err == -ENODATA) goto out; @@ -158,12 +158,12 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt, * Make sure that the stored uuid matches the uuid of the lower * layer where file handle will be decoded. */ - if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid)) + if (!uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid)) return NULL; - bytes = (fh->len - offsetof(struct ovl_fh, fid)); - real = exportfs_decode_fh(mnt, (struct fid *)fh->fid, - bytes >> 2, (int)fh->type, + bytes = (fh->fb.len - offsetof(struct ovl_fb, fid)); + real = exportfs_decode_fh(mnt, (struct fid *)fh->fb.fid, + bytes >> 2, (int)fh->fb.type, connected ? ovl_acceptable : NULL, mnt); if (IS_ERR(real)) { /* @@ -173,7 +173,7 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt, * index entries correctly. */ if (real == ERR_PTR(-ESTALE) && - !(fh->flags & OVL_FH_FLAG_PATH_UPPER)) + !(fh->fb.flags & OVL_FH_FLAG_PATH_UPPER)) real = NULL; return real; } @@ -323,6 +323,14 @@ int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected, int i; for (i = 0; i < ofs->numlower; i++) { + /* + * If lower fs uuid is not unique among lower fs we cannot match + * fh->uuid to layer. + */ + if (ofs->lower_layers[i].fsid && + ofs->lower_layers[i].fs->bad_uuid) + continue; + origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt, connected); if (origin) @@ -400,7 +408,7 @@ static int ovl_verify_fh(struct dentry *dentry, const char *name, if (IS_ERR(ofh)) return PTR_ERR(ofh); - if (fh->len != ofh->len || memcmp(fh, ofh, fh->len)) + if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.len)) err = -ESTALE; kfree(ofh); @@ -431,7 +439,7 @@ int ovl_verify_set_fh(struct dentry *dentry, const char *name, err = ovl_verify_fh(dentry, name, fh); if (set && err == -ENODATA) - err = ovl_do_setxattr(dentry, name, fh, fh->len, 0); + err = ovl_do_setxattr(dentry, name, fh->buf, fh->fb.len, 0); if (err) goto fail; @@ -505,20 +513,20 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index) goto fail; err = -EINVAL; - if (index->d_name.len < sizeof(struct ovl_fh)*2) + if (index->d_name.len < sizeof(struct ovl_fb)*2) goto fail; err = -ENOMEM; len = index->d_name.len / 2; - fh = kzalloc(len, GFP_KERNEL); + fh = kzalloc(len + OVL_FH_WIRE_OFFSET, GFP_KERNEL); if (!fh) goto fail; err = -EINVAL; - if (hex2bin((u8 *)fh, index->d_name.name, len)) + if (hex2bin(fh->buf, index->d_name.name, len)) goto fail; - err = ovl_check_fh_len(fh, len); + err = ovl_check_fb_len(&fh->fb, len); if (err) goto fail; @@ -597,11 +605,11 @@ static int ovl_get_index_name_fh(struct ovl_fh *fh, struct qstr *name) { char *n, *s; - n = kcalloc(fh->len, 2, GFP_KERNEL); + n = kcalloc(fh->fb.len, 2, GFP_KERNEL); if (!n) return -ENOMEM; - s = bin2hex(n, fh, fh->len); + s = bin2hex(n, fh->buf, fh->fb.len); *name = (struct qstr) QSTR_INIT(n, s - n); return 0; diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 6934bcf030f0..f283b1d69a9e 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -71,20 +71,36 @@ enum ovl_entry_flag { #error Endianness not defined #endif -/* The type returned by overlay exportfs ops when encoding an ovl_fh handle */ -#define OVL_FILEID 0xfb +/* The type used to be returned by overlay exportfs for misaligned fid */ +#define OVL_FILEID_V0 0xfb +/* The type returned by overlay exportfs for 32bit aligned fid */ +#define OVL_FILEID_V1 0xf8 -/* On-disk and in-memeory format for redirect by file handle */ -struct ovl_fh { +/* On-disk format for "origin" file handle */ +struct ovl_fb { u8 version; /* 0 */ u8 magic; /* 0xfb */ u8 len; /* size of this header + size of fid */ u8 flags; /* OVL_FH_FLAG_* */ u8 type; /* fid_type of fid */ uuid_t uuid; /* uuid of filesystem */ - u8 fid[0]; /* file identifier */ + u32 fid[0]; /* file identifier should be 32bit aligned in-memory */ } __packed; +/* In-memory and on-wire format for overlay file handle */ +struct ovl_fh { + u8 padding[3]; /* make sure fb.fid is 32bit aligned */ + union { + struct ovl_fb fb; + u8 buf[0]; + }; +} __packed; + +#define OVL_FH_WIRE_OFFSET offsetof(struct ovl_fh, fb) +#define OVL_FH_LEN(fh) (OVL_FH_WIRE_OFFSET + (fh)->fb.len) +#define OVL_FH_FID_OFFSET (OVL_FH_WIRE_OFFSET + \ + offsetof(struct ovl_fb, fid)) + static inline int ovl_do_rmdir(struct inode *dir, struct dentry *dentry) { int err = vfs_rmdir(dir, dentry); @@ -302,7 +318,13 @@ static inline void ovl_inode_unlock(struct inode *inode) /* namei.c */ -int ovl_check_fh_len(struct ovl_fh *fh, int fh_len); +int ovl_check_fb_len(struct ovl_fb *fb, int fb_len); + +static inline int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) +{ + return ovl_check_fb_len(&fh->fb, fh_len - OVL_FH_WIRE_OFFSET); +} + struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt, bool connected); int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected, diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h index a8279280e88d..28348c44ea5b 100644 --- a/fs/overlayfs/ovl_entry.h +++ b/fs/overlayfs/ovl_entry.h @@ -22,6 +22,8 @@ struct ovl_config { struct ovl_sb { struct super_block *sb; dev_t pseudo_dev; + /* Unusable (conflicting) uuid */ + bool bad_uuid; }; struct ovl_layer { diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index afbcb116a7f1..7621ff176d15 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1255,7 +1255,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) { unsigned int i; - if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt)) + if (!ofs->config.nfs_export && !ofs->upper_mnt) return true; for (i = 0; i < ofs->numlowerfs; i++) { @@ -1263,9 +1263,13 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) * We use uuid to associate an overlay lower file handle with a * lower layer, so we can accept lower fs with null uuid as long * as all lower layers with null uuid are on the same fs. + * if we detect multiple lower fs with the same uuid, we + * disable lower file handle decoding on all of them. */ - if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) + if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) { + ofs->lower_fs[i].bad_uuid = true; return false; + } } return true; } @@ -1277,6 +1281,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) unsigned int i; dev_t dev; int err; + bool bad_uuid = false; /* fsid 0 is reserved for upper fs even with non upper overlay */ if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb) @@ -1288,11 +1293,15 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) } if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { - ofs->config.index = false; - ofs->config.nfs_export = false; - pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n", - uuid_is_null(&sb->s_uuid) ? "null" : "conflicting", - path->dentry); + bad_uuid = true; + if (ofs->config.index || ofs->config.nfs_export) { + ofs->config.index = false; + ofs->config.nfs_export = false; + pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n", + uuid_is_null(&sb->s_uuid) ? "null" : + "conflicting", + path->dentry); + } } err = get_anon_bdev(&dev); @@ -1303,6 +1312,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) ofs->lower_fs[ofs->numlowerfs].sb = sb; ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev; + ofs->lower_fs[ofs->numlowerfs].bad_uuid = bad_uuid; ofs->numlowerfs++; return ofs->numlowerfs;