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path: root/hurd/io_path.mdwn
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 ``` ``````[[!meta copyright="Copyright © 2008 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU_Free_Documentation_License|/fdl]]."]]"""]] # read * [[glibc]]'s `read` is in `glibc/sysdeps/mach/hurd/read.c:__libc_read`. * That calls `glibc/hurd/fd-read.c:_hurd_fd_read()`. * That calls `__io_read`, which is an [[RPC]], i.e., that actually results into the [[translator/ext2fs]] server calling `hurd/libdiskfs/io-read.c:diskfs_S_io_read`. * That calls `_diskfs_rdwr_internal`, which calls `hurd/libpager/pager-memcpy.c:pager_memcpy`, which usually basically just tell the kernel to virtually project the memory object corresponding to the file in the caller process's memory. No read is actually done. * Then, when the process actually reads the data, the kernel gets the user page fault (`gnumach/i386/i386/trap.c:user_trap`), which calls `vm_fault`, etc., until actually getting to `gnumach/vm/vm_fault/vm_fault_page` which eventually calls `memory_object_data_request`, which is an [[RPC]], i.e., that actually results into the [[translator/ext2fs]] server calling `hurd/libpager/data-request.c:_pager_seqnos_memory_object_data_request`. * That calls `hurd/ext2fs/pager.c:pager_read_page`, which looks for where the data is on the disk, and eventually calls `hurd/libstore/rdwr.c:store_read`, which eventually calls `device_read`, which is an [[RPC]], i.e., that actually gets into the kernel calling `gnumach/linux/dev/glue/block.c:device_read`. * ext2fs eventually finishes the data_request() function, the kernel installs the page into the process that got a fault. ``````