gdb调试vfs read流程-zhenchengjin-ChinaUnix博客

调用df -h命令首先会执行execve，读取/bin/df文件，整个流程如下，其中涉及到了预读，页缓存及block层。

vfs read流程：

#0 submit_bio (rw=0, bio=0xf45c8880) at block/blk-core.c:1694

#1 0xc051605a in mpage_bio_submit (mapping=0xf3616840, pages=0xf59cfd6c, nr_pages=,

get_block=0xc055f7c1 ) at fs/mpage.c:77

#2 mpage_readpages (mapping=0xf3616840, pages=0xf59cfd6c, nr_pages=,

get_block=0xc055f7c1 ) at fs/mpage.c:394

#3 0xc055cb5b in ext4_readpages (file=, mapping=, pages=,

nr_pages=4) at fs/ext4/inode.c:2676

#4 0xc04b9a8a in read_pages (mapping=0xf3616840, filp=0xf455e300, offset=4, nr_to_read=4, lookahead_size=3)

at mm/readahead.c:119

#5 __do_page_cache_readahead (mapping=0xf3616840, filp=0xf455e300, offset=4, nr_to_read=4, lookahead_size=3)

at mm/readahead.c:199

#6 0xc04b9cf9 in ra_submit (ra=, mapping=0xf3616840, filp=) at mm/readahead.c:256

#7 0xc04b9e98 in ondemand_readahead (mapping=0xf3616840, ra=0xf455e34c, filp=0xf455e300, hit_readahead_marker=false,

offset=0, req_size=1) at mm/readahead.c:486

#8 0xc04b9f58 in page_cache_sync_readahead (mapping=, ra=, filp=0xf455e300,

offset=0, req_size=1) at mm/readahead.c:518

#9 page_cache_sync_readahead (mapping=, ra=, filp=0xf455e300, offset=0,

req_size=1) at mm/readahead.c:503

#10 0xc04b2fb6 in do_generic_file_read (iocb=0xf3616840, iov=0xf59cfefc, nr_segs=1, pos=0) at mm/filemap.c:1119

#11 generic_file_aio_read (iocb=0xf3616840, iov=0xf59cfefc, nr_segs=1, pos=0) at mm/filemap.c:1474

#12 0xc04ede8f in do_sync_read (filp=0xf455e300, buf=, len=, ppos=0xf59cff38)

at fs/read_write.c:350

#13 0xc04ee666 in vfs_read (file=0xf455e300, buf=0xf51c8b00 "", count=128, pos=0xf59cff38) at fs/read_write.c:379

#14 0xc04f25ce in kernel_read (file=, offset=, addr=0xf51c8b00 "", count=128)

at fs/exec.c:810

#15 0xc04f26bb in prepare_binprm (bprm=0xf51c8b00) at fs/exec.c:1314

#16 0xc04f38e6 in do_execve_common (filename=0xf4507000 "/bin/df", __argv=0x8c30140, __envp=0x8c1c158, regs=0xf59cffb4)

at fs/exec.c:1522

#17 do_execve (filename=0xf4507000 "/bin/df", __argv=0x8c30140, __envp=0x8c1c158, regs=0xf59cffb4) at fs/exec.c:1586

#18 0xc0408f6a in sys_execve (name=, argv=, envp=,

regs=0xf59cffb4) at arch/x86/kernel/process.c:317

结束流程，主要是设置读取到的页面的uptodate状态:

#0 mpage_end_io (bio=0xf45c8880, err=0) at fs/mpage.c:45

#1 0xc051128d in bio_endio (bio=, error=) at fs/bio.c:1451

#2 0xc05da649 in req_bio_endio (rq=0xf51bd000, bio=0xf45c8880, nbytes=, error=0)

at block/blk-core.c:176

#3 0xc05da795 in blk_update_request (req=0xf51bd000, error=0, nr_bytes=16384) at block/blk-core.c:2148

#4 0xc05dc2c0 in blk_update_bidi_request (rq=0xf51bd000, error=0, nr_bytes=, bidi_bytes=0)

at block/blk-core.c:2249

#5 0xc05dcfb9 in blk_end_bidi_request (rq=0xf51bd000, error=0, nr_bytes=, bidi_bytes=0)

at block/blk-core.c:2337

#6 0xc05dd006 in blk_end_request (rq=, error=, nr_bytes=)

at block/blk-core.c:2389

#7 0xc06af20a in scsi_end_request (cmd=0xf455e900, good_bytes=16384) at drivers/scsi/scsi_lib.c:554

#8 scsi_io_completion (cmd=0xf455e900, good_bytes=16384) at drivers/scsi/scsi_lib.c:826

#9 0xc06a83dc in scsi_finish_command (cmd=0xf455e900) at drivers/scsi/scsi.c:847

#10 0xc06aefad in scsi_softirq_done (rq=) at drivers/scsi/scsi_lib.c:1467

#11 0xc05e0e45 in blk_done_softirq (h=) at block/blk-softirq.c:34