linux.git/fs/btrfs/struct-funcs.c, branch v5.8

btrfs: update documentation of set/get helpers

2020-05-25T09:25:35+00:00

Signed-off-by: David Sterba

btrfs: optimize split page write in btrfs_set_token_##bits

2020-05-25T09:25:34+00:00

The fallback path calls helper write_extent_buffer to do write of the
data spanning two extent buffer pages. As the size is known, we can do
the write directly in two steps.  This removes one function call and
compiler can optimize memcpy as the sizes are known at compile time. The
cached token address is set to the second page.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: optimize split page write in btrfs_set_##bits

2020-05-25T09:25:34+00:00

The helper write_extent_buffer is called to do write of the data
spanning two extent buffer pages. As the size is known, we can do the
write directly in two steps.  This removes one function call and
compiler can optimize memcpy as the sizes are known at compile time.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: optimize split page read in btrfs_get_token_##bits

2020-05-25T09:25:34+00:00

The fallback path calls helper read_extent_buffer to do read of the data
spanning two extent buffer pages. As the size is known, we can do the
read directly in two steps.  This removes one function call and compiler
can optimize memcpy as the sizes are known at compile time. The cached
token address is set to the second page.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: optimize split page read in btrfs_get_##bits

2020-05-25T09:25:34+00:00

The helper read_extent_buffer is called to do read of the data spanning
two extent buffer pages. As the size is known, we can do the read
directly in two steps.  This removes one function call and compiler can
optimize memcpy as the sizes are known at compile time.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: constify extent_buffer in the API functions

2020-05-25T09:25:34+00:00

There are many helpers around extent buffers, found in extent_io.h and
ctree.h. Most of them can be converted to take constified eb as there
are no changes to the extent buffer structure itself but rather the
pages.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: speed up btrfs_set_token_##bits helpers

2020-05-25T09:25:33+00:00

The set/get token helpers either use the cached address in the token or
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. The token address is updated to the page, or the on
the next index, expecting that the next write will use that.

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

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: speed up btrfs_set_##bits helpers

2020-05-25T09:25:33+00:00

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 
Signed-off-by: David Sterba

btrfs: speed up btrfs_get_token_##bits helpers

2020-05-25T09:25:33+00:00

The set/get token helpers either use the cached address in the token or
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 read to get
data within a page, or fall back to read_extent_buffer that can handle
reads spanning more pages.

This is all wasteful. We know the number of bytes to read, 1/2/4/8 and
can find out the page. Then simply check if it's contained or the
fallback is needed. The token address is updated to the page, or the on
the next index, expecting that the next read will use that.

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

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: speed up btrfs_get_##bits helpers

2020-05-25T09:25:32+00:00

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
read to get data within a page, or fall back to read_extent_buffer that
can handle reads spanning more pages.

This is all wasteful. We know the number of bytes to read, 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 
Signed-off-by: David Sterba