pm24.git/fs/overlayfs, branch v4.17

ovl: add support for "xino" mount and config options

2018-04-12T10:04:50Z

With mount option "xino=on", mounter declares that there are enough free high bits in underlying fs to hold the layer fsid. If overlayfs does encounter underlying inodes using the high xino bits reserved for layer fsid, a warning will be emitted and the original inode number will be used. The mount option name "xino" goes after a similar meaning mount option of aufs, but in overlayfs case, the mapping is stateless. An example for a use case of "xino=on" is when upper/lower is on an xfs filesystem. xfs uses 64bit inode numbers, but it currently never uses the upper 8bit for inode numbers exposed via stat(2) and that is not likely to change in the future without user opting-in for a new xfs feature. The actual number of unused upper bit is much larger and determined by the xfs filesystem geometry (64 - agno_log - agblklog - inopblog). That means that for all practical purpose, there are enough unused bits in xfs inode numbers for more than OVL_MAX_STACK unique fsid's. Another use case of "xino=on" is when upper/lower is on tmpfs. tmpfs inode numbers are allocated sequentially since boot, so they will practially never use the high inode number bits. For compatibility with applications that expect 32bit inodes, the feature can be disabled with "xino=off". The option "xino=auto" automatically detects underlying filesystem that use 32bit inodes and enables the feature. The Kconfig option OVERLAY_FS_XINO_AUTO and module parameter of the same name, determine if the default mode for overlayfs mount is "xino=auto" or "xino=off". Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: consistent d_ino for non-samefs with xino

2018-04-12T10:04:50Z

When overlay layers are not all on the same fs, but all inode numbers of underlying fs do not use the high 'xino' bits, overlay st_ino values are constant and persistent. In that case, relax non-samefs constraint for consistent d_ino and always iterate non-merge dir using ovl_fill_real() actor so we can remap lower inode numbers to unique lower fs range. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: consistent i_ino for non-samefs with xino

2018-04-12T10:04:50Z

When overlay layers are not all on the same fs, but all inode numbers of underlying fs do not use the high 'xino' bits, overlay st_ino values are constant and persistent. In that case, set i_ino value to the same value as st_ino for nfsd readdirplus validator. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: constant st_ino for non-samefs with xino

2018-04-12T10:04:50Z

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 Signed-off-by: Miklos Szeredi

ovl: allocate anon bdev per unique lower fs

2018-04-12T10:04:50Z

Instead of allocating an anonymous bdev per lower layer, allocate one anonymous bdev per every unique lower fs that is different than upper fs. Every unique lower fs is assigned an fsid > 0 and the number of unique lower fs are stored in ofs->numlowerfs. The assigned fsid is stored in the lower layer struct and will be used also for inode number multiplexing. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: factor out ovl_map_dev_ino() helper

2018-04-12T10:04:50Z

A helper for ovl_getattr() to map the values of st_dev and st_ino according to constant st_ino rules. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: cleanup ovl_update_time()

2018-04-12T10:04:50Z

No need to mess with an alias, the upperdentry can be retrieved directly from the overlay inode. Signed-off-by: Miklos Szeredi

ovl: add WARN_ON() for non-dir redirect cases

2018-04-12T10:04:49Z

Signed-off-by: Miklos Szeredi

ovl: cleanup setting OVL_INDEX

2018-04-12T10:04:49Z

Signed-off-by: Miklos Szeredi

ovl: set d->is_dir and d->opaque for last path element

2018-04-12T10:04:49Z

Certain properties in ovl_lookup_data should be set only for the last element of the path. IOW, if we are calling ovl_lookup_single() for an absolute redirect, then d->is_dir and d->opaque do not make much sense for intermediate path elements. Instead set them only if dentry being lookup is last path element. As of now we do not seem to be making use of d->opaque if it is set for a path/dentry in lower. But just define the semantics so that future code can make use of this assumption. Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi