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ovl: constant st_ino for non-samefs with xino

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On 64bit systems, when overlay layers are not all on the same fs, but
all inode numbers of underlying fs are not using the high bits, use the
high bits to partition the overlay st_ino address space.  The high bits
hold the fsid (upper fsid is 0).  This way overlay inode numbers are unique
and all inodes use overlay st_dev.  Inode numbers are also persistent
for a given layer configuration.

Currently, our only indication for available high ino bits is from a
filesystem that supports file handles and uses the default encode_fh()
operation, which encodes a 32bit inode number.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Amir Goldstein
2017-11-07 13:55:04 +02:00
committed by Miklos Szeredi
parent 5148626b80
commit e487d889b7
5 changed files with 75 additions and 10 deletions
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2
fs/overlayfs/ovl_entry.h
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@@ -63,6 +63,8 @@ struct ovl_fs {
/* Did we take the inuse lock? */
bool upperdir_locked;
bool workdir_locked;
/* Inode numbers in all layers do not use the high xino_bits */
unsigned int xino_bits;
};
/* private information held for every overlayfs dentry */