函数逻辑报告

Linux Kernel

v5.5.9

Brick Technologies Co., Ltd

Source Code:fs\direct-io.c Create Date:2022-07-29 10:46:36
Last Modify:2020-03-12 14:18:49 Copyright©Brick
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函数名称：Walk the user pages, and the file, mapping blocks to disk and generating* a sequence of (page,offset,len,block) mappings. These mappings are injected* into submit_page_section(), which takes care of the next stage of submission

函数原型：static int do_direct_IO(struct dio *dio, struct dio_submit *sdio, struct buffer_head *map_bh)

返回类型：int

参数：

类型参数名称
struct dio *dio
struct dio_submit *sdio
struct buffer_head *map_bh
946  blkbits等于doesn't change
947  i_blkbits等于blkbits加When we're using an alignment whichis finer than the filesystem's softblocksize, this specifies how muchfiner. blkfactor=2 means 1/4-blockalignment. Does not change
948  ret等于0
950  当Current offset into the underlyingfile in dio_block units. 小于doesn't change 循环
954  page等于Get another userspace page. Returns an ERR_PTR on error. Pages are* buffered inside the dio so that we can call get_user_pages() against a* decent number of pages, less frequently. To provide nicer use of the* L1 cache.
955  如果是错误则
956  ret等于错误
957  转到:out
959  from等于如果xt page to process 则0否则from
960  to等于如果xt page to process 恒等于last valid page + 1 减1则to否则PAGE_SIZE
961  xt page to process 自加
963  当from小于to循环
968  如果At block_in_file. changes 恒等于0则
975  ret等于Call into the fs to map some more disk blocks. We record the current number* of available blocks at sdio->blocks_available. These are in units of the* fs blocksize, i_blocksize(inode).* The fs is allowed to map lots of blocks at once
976  如果ret则
980  如果非buffer_mapped(map_bh)则转到:do_holes
983  At block_in_file. changes 等于 size of mapping 右移blkbits位
985  xt block to be put under IO,in dio_blocks units 等于 start block number 左移When we're using an alignment whichis finer than the filesystem's softblocksize, this specifies how muchfiner. blkfactor=2 means 1/4-blockalignment. Does not change 位
987  如果buffer_new(map_bh)则
994  如果非When we're using an alignment whichis finer than the filesystem's softblocksize, this specifies how muchfiner. blkfactor=2 means 1/4-blockalignment. Does not change 则转到:do_holes
997  blkmask等于1左移When we're using an alignment whichis finer than the filesystem's softblocksize, this specifies how muchfiner. blkfactor=2 means 1/4-blockalignment. Does not change 位的值减1
998  dio_remainder等于Current offset into the underlyingfile in dio_block units. 按位与blkmask
1011  如果非buffer_new(map_bh)则xt block to be put under IO,in dio_blocks units 加等于dio_remainder
1013  At block_in_file. changes 减等于dio_remainder
1015  do_holes :
1017  如果非buffer_mapped(map_bh)则
1050  如果此条件成立可能性小(为编译器优化)(When we're using an alignment whichis finer than the filesystem's softblocksize, this specifies how muchfiner. blkfactor=2 means 1/4-blockalignment. Does not change && !lag: sub-blocksize zeroing hasbeen performed at the start of awrite )则If we are not writing the entire block and get_block() allocated* the block for us, we need to fill-in the unused portion of the* block with zeros
1057  this_chunk_blocks等于At block_in_file. changes
1058  u等于to减from右移blkbits位
1059  如果this_chunk_blocks大于u则this_chunk_blocks等于u
1061  u等于doesn't change 减Current offset into the underlyingfile in dio_block units.
1062  如果this_chunk_blocks大于u则this_chunk_blocks等于u
1064  this_chunk_bytes等于this_chunk_blocks左移blkbits位
1065  BUG_ON(this_chunk_bytes == 0)
1067  如果this_chunk_blocks恒等于At block_in_file. changes 则prev block is at a boundary 等于buffer_boundary(map_bh)
1069  ret等于An autonomous function to put a chunk of a page under deferred IO.* The caller doesn't actually know (or care) whether this piece of page is in* a BIO, or is under IO or whatever. We just take care of all possible * situations here
1074  如果ret则
1078  xt block to be put under IO,in dio_blocks units 加等于this_chunk_blocks
1080  Current offset into the underlyingfile in dio_block units. 加等于this_chunk_blocks
1081  from加等于this_chunk_bytes
1082  IO result 加等于this_chunk_bytes
1083  At block_in_file. changes 减等于this_chunk_blocks
1084  next_block :
1085  BUG_ON(Current offset into the underlyingfile in dio_block units. > doesn't change )
1086  如果Current offset into the underlyingfile in dio_block units. 恒等于doesn't change 则退出
1091  Perform a free_page(), also freeing any swap cache associated with* this page if it is the last user of the page.
1093  out :
1094  返回:ret
调用者
名称描述
do_blockdev_direct_IOThis is a library function for use by filesystem drivers