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In LU-13031 the JobID of the process that first creates a file is stored in the user.job xattr on the MDT inode, for diagnostic purposes and to allow determining provenance of each file later on.  For the Trash Can, LU-17648 describes storing the JobID of the process that is deleting the file, for diagnostics such as determining rogue processes that are deleting files in the filesystem.  Something like user.del would be a reasonable default xattr name.  The actual xattr name can be configured with the mdt.*.job_xattr_del parameter.

Backup and Restore of MDT with Trash Can

For filesystem-level/namespace backup and restore, the .Trash directory will not be visible to the backup utility during namespace traversal, so deleted files in the Trash will not be backed up.

For MDT-level/device backup and restore, the Trash directory and its contents will be backed up in the same way as any other directory in the filesystem.  The stub pFID directory is named by the parent directory FID, so it will be backed up and restored as-is (its FID is not really important, but should be treated normally).  The FID on the actual parent directory will be preserved in the trusted.lma xattr, but the FID lookup in the restored OI will not be possible until after the initial post-restore OI Scrub has completed.  Otherwise, the FID lookup in the restored OI will reference the old inode number, which will reference a wrong or unused inode number/generation, and should return -EINPROGRESS or possibly -ESTALE.

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It may be necessary to add special support to OI Scrub/LFSCK to handle the Trash directory on each MDT, so that it can do a top-level scan of the stub pFID directories to confirm that the parent FID still references a valid parent directory.

Virtual .Trash Directory Support 

Virtual .Trash

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directory

It would useful to implement a A virtual ".Trash" subdirectory accessible in each directory in the filesystem that can be used to browse would allow users to easily browse deleted files/directories under the current subdirectory in the Trash Can and access them for recovery.

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