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Brian Foster
2a4e749760
The bcachefs folio writeback code includes a bio full check as well as a fixed size check to determine when to split off and submit writeback I/O. The inclusive check of the latter against the limit means that writeback can submit slightly prematurely. This is not a functional problem, but results in unnecessarily split I/Os and extent merging. This can be observed with a buffered write sized exactly to the current maximum value (1MB) and with key_merging_disabled=1. The latter prevents the merge from the second write such that a subsequent check of the extent list shows a 1020k extent followed by a contiguous 4k extent. The purpose for the fixed size check is also undocumented and somewhat obscure. Lift this check into a new helper that wraps the bio check, fix the comparison logic, and add a comment to document the purpose and how we might improve on this in the future. Signed-off-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Linux kernel
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