FIEMAP fixes for --is-reflink #531
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Aug 9, 2022
Test exit statuses 1, 3, 4, 6, 7, 8, and 9.
Completing the current loop iteration if the current extent is not contiguous with the last means the extent flags and file offset are updated as if the extents *were* contiguous. In general, this causes calling code to skip every second extent! Also remove a redundant write to file_offset_next that is always clobbered after the loop exits. Fixes sahib#527
There were two EOF checks in rm_util_link_type. One of them caused the last extent to be ignored in files with at least two extents. The other mishandled files that end with a hole. In rm_offset_get_from_fd, always warn about no extents at a nonzero file offset, since calling code should stop after the last extent. Fixes sahib#528
Holes are represented by logical gaps in the FIEMAP mapping. Summing the extent lengths to get a file offset causes file_offset to get out of sync. If the hole is smaller than the following extent, the next few FIEMAP calls may return the same extent. Fixes sahib#529
Holes are handled by ignoring them when they are after an extent and skipping them when they are before one. Since we were only comparing the current file position, a file with a hole could match a file without one as long as the physical offsets match and the extents logically end at the same place. This led to --is-reflink false-positives. Fix this by comparing the logical offset of each extent. Fixes sahib#611
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rmlint previously ignored holes between physically adjacent extents. This could cause files to be detected as reflinked that weren't, if one file had a complete extent and the other file had two pieces of it separated by a hole. Check for logical gaps as well as physical gaps to fix this problem. Fixes sahib#530
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This pull request is intended to fix the FIEMAP-related issues with --is-reflink: #527, #528, #529, and #530.