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9b23fdbd5d
There's an inherent race in taking a snapshot while an unlinked file is open, and then reattaching it in the child snapshot. In the interior snapshot node the file will appear unlinked, as though it should be deleted - it's not referenced by anything in that snapshot - but we can't delete it, because the file data is referenced by the child snapshot. This was being handled incorrectly with propagate_key_to_snapshot_leaves() - but that doesn't resolve the fundamental inconsistency of "this file looks like it should be deleted according to normal rules, but - ". To fix this, we need to fix the rule for when an inode is deleted. The previous rule, ignoring snapshots (there was no well-defined rule for with snapshots) was: Unlinked, non open files are deleted, either at recovery time or during online fsck The new rule is: Unlinked, non open files, that do not exist in child snapshots, are deleted. To make this work transactionally, we add a new inode flag, BCH_INODE_has_child_snapshot; it overrides BCH_INODE_unlinked when considering whether to delete an inode, or put it on the deleted list. For transactional consistency, clearing it handled by the inode trigger: when deleting an inode we check if there are parent inodes which can now have the BCH_INODE_has_child_snapshot flag cleared. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
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.