kernel.git/fs/overlayfs/util.c, branch linux-4.16.y

ovl: set i_ino to the value of st_ino for NFS export

2018-04-19T06:54:09Z

commit 695b46e76b62447e506cddc87e088236498008e5 upstream. Eddie Horng reported that readdir of an overlayfs directory that was exported via NFSv3 returns entries with d_type set to DT_UNKNOWN. The reason is that while preparing the response for readdirplus, nfsd checks inside encode_entryplus_baggage() that a child dentry's inode number matches the value of d_ino returns by overlayfs readdir iterator. Because the overlayfs inodes use arbitrary inode numbers that are not correlated with the values of st_ino/d_ino, NFSv3 falls back to not encoding d_type. Although this is an allowed behavior, we can fix it for the case of all overlayfs layers on the same underlying filesystem. When NFS export is enabled and d_ino is consistent with st_ino (samefs), set the same value also to i_ino in ovl_fill_inode() for all overlayfs inodes, nfsd readdirplus sanity checks will pass. ovl_fill_inode() may be called from ovl_new_inode(), before real inode was created with ino arg 0. In that case, i_ino will be updated to real upper inode i_ino on ovl_inode_init() or ovl_inode_update(). Reported-by: Eddie Horng Tested-by: Eddie Horng Signed-off-by: Amir Goldstein Fixes: 8383f1748829 ("ovl: wire up NFS export operations") Cc: #v4.16 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

ovl: store 'has_upper' and 'opaque' as bit flags

2018-01-24T10:25:58Z

We need to make some room in struct ovl_entry to store information about redirected ancestors for NFS export, so cram two booleans as bit flags. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: copy up of disconnected dentries

2018-01-24T10:25:58Z

With NFS export, some operations on decoded file handles (e.g. open, link, setattr, xattr_set) may call copy up with a disconnected non-dir. In this case, we will copy up lower inode to index dir without linking it to upper dir. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: whiteout index when union nlink drops to zero

2018-01-24T10:25:56Z

With NFS export feature enabled, when overlay inode nlink drops to zero, instead of removing the index entry, replace it with a whiteout index entry. This is needed for NFS export in order to prevent future open by handle from opening the lower file directly. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: cleanup dir index when dir nlink drops to zero

2018-01-24T10:25:55Z

When non-dir index union nlink drops to zero the non-dir index is cleaned. Do the same for directory type index entries when union directory is removed. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: index directories on copy up for NFS export

2018-01-24T10:25:55Z

With the NFS export feature enabled, all dirs are indexed on copy up. Non-dir files are copied up directly to indexdir and then hardlinked to upper dir. Directories are copied up to indexdir, then an index entry is created in indexdir with 'upper' xattr pointing to the copied up dir and then the copied up dir is moved to upper dir. Directory index is also used for consistency verification, like detecting multiple redirected dirs to the same lower dir on lookup. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: index all non-dir on copy up for NFS export

2018-01-24T10:25:54Z

With the NFS export feature enabled, all non-dir are indexed on copy up. The copy up origin inode of an indexed non-dir can be used as a unique identifier of the overlay object. The full index is also used for consistency verfication, like detecting multiple non-hardlink uppers with the same 'origin' on lookup. Directory index on copy up will be implemented by following patch. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: create ovl_need_index() helper

2018-01-24T10:25:54Z

The helper determines which lower file needs to be indexed on copy up and before nlink changes. For index=on, the helper evaluates to true for lower hardlinks. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: add support for "nfs_export" configuration

2018-01-24T10:25:37Z

Introduce the "nfs_export" config, module and mount options. The NFS export feature depends on the "index" feature and enables two implicit overlayfs features: "index_all" and "verify_lower". The "index_all" feature creates an index on copy up of every file and directory. The "verify_lower" feature uses the full index to detect overlay filesystems inconsistencies on lookup, like redirect from multiple upper dirs to the same lower dir. NFS export can be enabled for non-upper mount with no index. However, because lower layer redirects cannot be verified with the index, enabling NFS export support on an overlay with no upper layer requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The full index may incur some overhead on mount time, especially when verifying that lower directory file handles are not stale. NFS export support, full index and consistency verification will be implemented by following patches. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: hash directory inodes for fsnotify

2018-01-19T12:54:33Z

fsnotify pins a watched directory inode in cache, but if directory dentry is released, new lookup will allocate a new dentry and a new inode. Directory events will be notified on the new inode, while fsnotify listener is watching the old pinned inode. Hash all directory inodes to reuse the pinned inode on lookup. Pure upper dirs are hashes by real upper inode, merge and lower dirs are hashed by real lower inode. The reference to lower inode was being held by the lower dentry object in the overlay dentry (oe->lowerstack[0]). Releasing the overlay dentry may drop lower inode refcount to zero. Add a refcount on behalf of the overlay inode to prevent that. As a by-product, hashing directory inodes also detects multiple redirected dirs to the same lower dir and uncovered redirected dir target on and returns -ESTALE on lookup. The reported issue dates back to initial version of overlayfs, but this patch depends on ovl_inode code that was introduced in kernel v4.13. Cc: #v4.13 Reported-by: Niklas Cassel Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi Tested-by: Niklas Cassel