btrfs: speed up btrfs_set_##bits helpers

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The helpers unconditionally call map_private_extent_buffer to get the
address of page containing the requested offset plus the mapping start
and length. Depending on the return value, the fast path uses unaligned
put to write data within a page, or fall back to write_extent_buffer
that can handle writes spanning more pages.

This is all wasteful. We know the number of bytes to write, 1/2/4/8 and
can find out the page. Then simply check if it's contained or the
fallback is needed.

This saves one function call to map_private_extent_buffer and several
unnecessary temporary variables.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

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This commit is contained in:

David Sterba 2020-04-29 18:07:04 +02:00

parent 8f9da810ee

commit 029e4a42a2

1 changed files with 10 additions and 17 deletions

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27

fs/btrfs/struct-funcs.c

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