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Currently an incremental snapshot can generate link operations which
contain an invalid target path. Such case happens when in the send
snapshot a file was renamed, a new hard link added for it and some
other inode (with a lower number) got renamed to the former name of
that file. Example:
Parent snapshot
. (ino 256)
|
|--- f1 (ino 257)
|--- f2 (ino 258)
|--- f3 (ino 259)
Send snapshot
. (ino 256)
|
|--- f2 (ino 257)
|--- f3 (ino 258)
|--- f4 (ino 259)
|--- f5 (ino 258)
The following steps happen when computing the incremental send stream:
1) When processing inode 257, inode 258 is orphanized (renamed to
"o258-7-0"), because its current reference has the same name as the
new reference for inode 257;
2) When processing inode 258, we iterate over all its new references,
which have the names "f3" and "f5". The first iteration sees name
"f5" and renames the inode from its orphan name ("o258-7-0") to
"f5", while the second iteration sees the name "f3" and, incorrectly,
issues a link operation with a target name matching the orphan name,
which no longer exists. The first iteration had reset the current
valid path of the inode to "f5", but in the second iteration we lost
it because we found another inode, with a higher number of 259, which
has a reference named "f3" as well, so we orphanized inode 259 and
recomputed the current valid path of inode 258 to its old orphan
name because inode 259 could be an ancestor of inode 258 and therefore
the current valid path could contain the pre-orphanization name of
inode 259. However in this case inode 259 is not an ancestor of inode
258 so the current valid path should not be recomputed.
This makes the receiver fail with the following error:
ERROR: link f3 -> o258-7-0 failed: No such file or directory
So fix this by not recomputing the current valid path for an inode
whenever we find a colliding reference from some not yet processed inode
(inode number higher then the one currently being processed), unless
that other inode is an ancestor of the one we are currently processing.
A test case for fstests will follow soon.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.