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author | Chris Mason <chris.mason@oracle.com> | 2008-09-29 19:18:18 (GMT) |
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committer | Chris Mason <chris.mason@oracle.com> | 2008-09-29 19:18:18 (GMT) |
commit | d352ac68148b69937d39ca5d48bcc4478e118dbf (patch) | |
tree | 7951dd7311999d9e77766acdc7f8e93de97874d8 /fs/btrfs/struct-funcs.c | |
parent | 9a5e1ea1e1e539e244a54afffc330fc368376ab9 (diff) | |
download | linux-fsl-qoriq-d352ac68148b69937d39ca5d48bcc4478e118dbf.tar.xz |
Btrfs: add and improve comments
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>
Diffstat (limited to 'fs/btrfs/struct-funcs.c')
-rw-r--r-- | fs/btrfs/struct-funcs.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c index ad03a32..cdedbe1 100644 --- a/fs/btrfs/struct-funcs.c +++ b/fs/btrfs/struct-funcs.c @@ -17,6 +17,27 @@ */ #include <linux/highmem.h> + +/* this is some deeply nasty code. ctree.h has a different + * definition for this BTRFS_SETGET_FUNCS macro, behind a #ifndef + * + * The end result is that anyone who #includes ctree.h gets a + * declaration for the btrfs_set_foo functions and btrfs_foo functions + * + * This file declares the macros and then #includes ctree.h, which results + * in cpp creating the function here based on the template below. + * + * These setget functions do all the extent_buffer related mapping + * required to efficiently read and write specific fields in the extent + * buffers. Every pointer to metadata items in btrfs is really just + * an unsigned long offset into the extent buffer which has been + * cast to a specific type. This gives us all the gcc type checking. + * + * The extent buffer api is used to do all the kmapping and page + * spanning work required to get extent buffers in highmem and have + * a metadata blocksize different from the page size. + */ + #define BTRFS_SETGET_FUNCS(name, type, member, bits) \ u##bits btrfs_##name(struct extent_buffer *eb, \ type *s) \ |