Checking Undelete Flag

In order to treat the files with the undelete flag in a special way, we had to check whether that flag was indeed set on a specific file.  We first had to create the undelete filesystem flag.  The next available bit combination was the one corresponding to 1024, which we then used and named it S_UNDELETE. The next step was to check the presence of the flag.  This was achieved by writing the macro IS_UNDELETE in linux/fs.h that executes a bitwise or between the inode's flags field and the S_UNDELETE flag.
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