ext4: fix wrong span for an internal node's last child - #420
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deitch merged 1 commit intoAug 3, 2026
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extentInternalNode.findBlocks and .blocks() called parseExtents with an inclusive end block in its count argument, but parseExtents' internal-node branch treats that argument as an actual count (start+count marks one past the end) when deriving the span of a node's last child -- real ext4 index entries don't store a count on disk, so the last entry's span has to come from the caller. The mismatch silently dropped the final file block of any range reaching the last child of a node loaded this way. .blocks() reads were unaffected in practice: leaf-node parsing ignores the start/count arguments entirely, so a wrong count only mattered when it was also passed down to a child's own findBlocks call. findBlocks itself isn't wired up to any current caller, so this had no observable effect until something exercises it directly (e.g. a range read added on top of the existing full-file read path). Pass the child's actual count instead of computing an end block, matching the one caller (loadChildNode) that already did this correctly. Signed-off-by: Austin Vazquez <austin.vazquez@docker.com>
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extentInternalNode.findBlocks and .blocks() called parseExtents with an inclusive end block in its count argument, but parseExtents' internal-node branch treats that argument as an actual count (start+count marks one past the end) when deriving the span of a node's last child -- real ext4 index entries don't store a count on disk, so the last entry's span has to come from the caller. The mismatch silently dropped the final file block of any range reaching the last child of a node loaded this way.
.blocks() reads were unaffected in practice: leaf-node parsing ignores the start/count arguments entirely, so a wrong count only mattered when it was also passed down to a child's own findBlocks call. findBlocks itself isn't wired up to any current caller, so this had no observable effect until something exercises it directly (e.g. a range read added on top of the existing full-file read path).
Pass the child's actual count instead of computing an end block, matching the one caller (loadChildNode) that already did this correctly.