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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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>
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The bounds checking is now done in map_private_extent_buffer but that
will be removed in following patches and some sanity checks should still
be done.
There are two separate checks to see the kind of out of bounds access:
partial (start offset is in the buffer) or complete (both start and end
are out).
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
All the set/get helpers first check if the token contains a cached
address. After first use the address is always valid, but the extra
check is done for each call.
The token initialization can optimistically set it to the first extent
buffer page, that we know always exists. Then the condition in all
btrfs_token_*/btrfs_set_token_* can be simplified by removing the
address check from the condition, but for development the assertion
still makes sure it's valid.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that all set/get helpers use the eb from the token, we don't need to
pass it to many btrfs_token_*/btrfs_set_token_* helpers, saving some
stack space.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The token stores a copy of the extent buffer pointer but does not make
any use of it besides sanity checks. We can use it and drop the eb
parameter from several functions, this patch only switches the use
inside the set/get helpers.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Further simplifaction of the get/set helpers is possible when the token
is uniquely tied to an extent buffer. A condition and an assignment can
be avoided.
The initializations are moved closer to the first use when the extent
buffer is valid. There's one exception in __push_leaf_left where the
token is reused.
Signed-off-by: David Sterba <dsterba@suse.com>
Now that we can safely assume that the token is always a valid pointer,
remove the branches that check that.
Signed-off-by: David Sterba <dsterba@suse.com>
There are helpers for all type widths defined via macro and optionally
can use a token which is a cached pointer to avoid repeated mapping of
the extent buffer.
The token value is known at compile time, when it's valid it's always
address of a local variable, otherwise it's NULL passed by the
token-less helpers.
This can be utilized to remove some branching as the helpers are used
frequenlty.
Signed-off-by: David Sterba <dsterba@suse.com>
Remove GPL boilerplate text (long, short, one-line) and keep the rest,
ie. personal, company or original source copyright statements. Add the
SPDX header.
Signed-off-by: David Sterba <dsterba@suse.com>
We have reader helpers for most of the on-disk structures that use
an extent_buffer and pointer as offset into the buffer that are
read-only. We should mark them as const and, in turn, allow consumers
of these interfaces to mark the buffers const as well.
No impact on code, but serves as documentation that a buffer is intended
not to be modified.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Mostly direct substitution with occasional adjustment or removing
outdated comments.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
BTRFS_SETGET_FUNCS macro is used to generate btrfs_set_foo() and
btrfs_foo() functions, which read and write specific fields in the
extent buffer.
The total number of set/get functions is ~200, but in fact we only
need 8 functions: 2 for u8 field, 2 for u16, 2 for u32 and 2 for u64.
It results in redunction of ~37K bytes.
text data bss dec hex filename
629661 12489 216 642366 9cd3e fs/btrfs/btrfs.o.orig
592637 12489 216 605342 93c9e fs/btrfs/btrfs.o
Signed-off-by: Li Zefan <lizefan@huawei.com>
The extent_buffers have a very complex interface where
we use HIGHMEM for metadata and try to cache a kmap mapping
to access the memory.
The next commit adds reader/writer locks, and concurrent use
of this kmap cache would make it even more complex.
This commit drops the ability to use HIGHMEM with extent buffers,
and rips out all of the related code.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The btrfs macros to access individual struct members on disk were
sending the same variable to functions that expected different types
of endianness. This fix explicitly creates a variable of the correct
type instead of abusing a single variable for mixed purposes.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This improves the comments at the top of many functions. It didn't
dive into the guts of functions because I was trying to
avoid merging problems with the new allocator and back reference work.
extent-tree.c and volumes.c were both skipped, and there is definitely
more work todo in cleaning and commenting the code.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Btrfs set/get macros lose type information needed to avoid
unaligned accesses on sparc64.
ere is a patch for the kernel bits which fixes most of the
unaligned accesses on sparc64.
btrfs_name_hash is modified to return the hash value instead
of getting a return location via a (potentially unaligned)
pointer.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
