EROFS uses NID to indicate the on-disk inode offset, which can
exceed 32 bits. However, the default encode_fh uses the ino32,
thus it doesn't work if the image is larger than 128GiB.
Let's introduce our own helpers to encode file handles.
It's easy to reproduce:
1. prepare an erofs image with nid bigger than U32_MAX
2. mount -t erofs foo.img /mnt/erofs
3. set exportfs with configuration: /mnt/erofs *(rw,sync,
no_root_squash)
4. mount -t nfs $IP:/mnt/erofs /mnt/nfs
5. md5sum /mnt/nfs/foo # foo is the file which nid bigger
than U32_MAX. # you will get ESTALE error.
In the case of overlayfs, the underlying filesystem's file
handle is encoded in ovl_fb.fid, which is similar to NFS's
case. If the NID of file is larger than U32_MAX, the overlay
will get -ESTALE error when calls exportfs_decode_fh.
Fixes: 3e917cc305c6 ("erofs: make filesystem exportable")
Signed-off-by: Hongbo Li <[email protected]>
---
v3: https://lore.kernel.org/all/[email protected]/
- Improve commit message readability as suggested by Xiang.
- Remove extra variable to make the code simpler as suggested
by Xiang.
v2: https://lore.kernel.org/all/[email protected]/
- Assign parent nid with correct value.
v1: https://lore.kernel.org/all/[email protected]/
- Encode generation into file handle and minor clean code.
- Update the commiti's title.
---
fs/erofs/super.c | 44 ++++++++++++++++++++++++++++++++++++--------
1 file changed, 36 insertions(+), 8 deletions(-)
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index cadec6b1b554..727e2fbaa168 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -511,24 +511,52 @@ static int erofs_fc_parse_param(struct fs_context *fc,
return 0;
}
-static struct inode *erofs_nfs_get_inode(struct super_block *sb,
- u64 ino, u32 generation)
+static int erofs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
+ struct inode *parent)
{
- return erofs_iget(sb, ino);
+ erofs_nid_t nid = EROFS_I(inode)->nid;
+ int len = parent ? 6 : 3;
+
+ if (*max_len < len) {
+ *max_len = len;
+ return FILEID_INVALID;
+ }
+
+ fh[0] = (u32)(nid >> 32);
+ fh[1] = (u32)(nid & 0xffffffff);
+ fh[2] = inode->i_generation;
+
+ if (parent) {
+ nid = EROFS_I(parent)->nid;
+
+ fh[3] = (u32)(nid >> 32);
+ fh[4] = (u32)(nid & 0xffffffff);
+ fh[5] = parent->i_generation;
+ }
+
+ *max_len = len;
+ return parent ? FILEID_INO64_GEN_PARENT : FILEID_INO64_GEN;
}
static struct dentry *erofs_fh_to_dentry(struct super_block *sb,
struct fid *fid, int fh_len, int fh_type)
{
- return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
- erofs_nfs_get_inode);
+ if ((fh_type != FILEID_INO64_GEN &&
+ fh_type != FILEID_INO64_GEN_PARENT) || fh_len < 3)
+ return NULL;
+
+ return d_obtain_alias(erofs_iget(sb,
+ ((u64)fid->raw[0] << 32) | fid->raw[1]));
}
static struct dentry *erofs_fh_to_parent(struct super_block *sb,
struct fid *fid, int fh_len, int fh_type)
{
- return generic_fh_to_parent(sb, fid, fh_len, fh_type,
- erofs_nfs_get_inode);
+ if (fh_type != FILEID_INO64_GEN_PARENT || fh_len < 6)
+ return NULL;
+
+ return d_obtain_alias(erofs_iget(sb,
+ ((u64)fid->raw[3] << 32) | fid->raw[4]));
}
static struct dentry *erofs_get_parent(struct dentry *child)
@@ -544,7 +572,7 @@ static struct dentry *erofs_get_parent(struct dentry *child)
}
static const struct export_operations erofs_export_ops = {
- .encode_fh = generic_encode_ino32_fh,
+ .encode_fh = erofs_encode_fh,
.fh_to_dentry = erofs_fh_to_dentry,
.fh_to_parent = erofs_fh_to_parent,
.get_parent = erofs_get_parent,
--
2.22.0
