diff --git a/0/linux/kernel/blk_drv/ll_rw_blk.c b/0/linux/kernel/blk_drv/ll_rw_blk.c new file mode 100644 index 0000000..f57d998 --- /dev/null +++ b/0/linux/kernel/blk_drv/ll_rw_blk.c @@ -0,0 +1,165 @@ +/* + * linux/kernel/blk_dev/ll_rw.c + * + * (C) 1991 Linus Torvalds + */ + +/* + * This handles all read/write requests to block devices + */ +#include +#include +#include +#include + +#include "blk.h" + +/* + * The request-struct contains all necessary data + * to load a nr of sectors into memory + */ +struct request request[NR_REQUEST]; + +/* + * used to wait on when there are no free requests + */ +struct task_struct * wait_for_request = NULL; + +/* blk_dev_struct is: + * do_request-address + * next-request + */ +struct blk_dev_struct blk_dev[NR_BLK_DEV] = { + { NULL, NULL }, /* no_dev */ + { NULL, NULL }, /* dev mem */ + { NULL, NULL }, /* dev fd */ + { NULL, NULL }, /* dev hd */ + { NULL, NULL }, /* dev ttyx */ + { NULL, NULL }, /* dev tty */ + { NULL, NULL } /* dev lp */ +}; + +static inline void lock_buffer(struct buffer_head * bh) +{ + cli(); + while (bh->b_lock) + sleep_on(&bh->b_wait); + bh->b_lock=1; + sti(); +} + +static inline void unlock_buffer(struct buffer_head * bh) +{ + if (!bh->b_lock) + printk("ll_rw_block.c: buffer not locked\n\r"); + bh->b_lock = 0; + wake_up(&bh->b_wait); +} + +/* + * add-request adds a request to the linked list. + * It disables interrupts so that it can muck with the + * request-lists in peace. + */ +static void add_request(struct blk_dev_struct * dev, struct request * req) +{ + struct request * tmp; + + req->next = NULL; + cli(); + if (req->bh) + req->bh->b_dirt = 0; + if (!(tmp = dev->current_request)) { + dev->current_request = req; + sti(); + (dev->request_fn)(); + return; + } + for ( ; tmp->next ; tmp=tmp->next) + if ((IN_ORDER(tmp,req) || + !IN_ORDER(tmp,tmp->next)) && + IN_ORDER(req,tmp->next)) + break; + req->next=tmp->next; + tmp->next=req; + sti(); +} + +static void make_request(int major,int rw, struct buffer_head * bh) +{ + struct request * req; + int rw_ahead; + +/* WRITEA/READA is special case - it is not really needed, so if the */ +/* buffer is locked, we just forget about it, else it's a normal read */ + if (rw_ahead = (rw == READA || rw == WRITEA)) { + if (bh->b_lock) + return; + if (rw == READA) + rw = READ; + else + rw = WRITE; + } + if (rw!=READ && rw!=WRITE) + panic("Bad block dev command, must be R/W/RA/WA"); + lock_buffer(bh); + if ((rw == WRITE && !bh->b_dirt) || (rw == READ && bh->b_uptodate)) { + unlock_buffer(bh); + return; + } +repeat: +/* we don't allow the write-requests to fill up the queue completely: + * we want some room for reads: they take precedence. The last third + * of the requests are only for reads. + */ + if (rw == READ) + req = request+NR_REQUEST; + else + req = request+((NR_REQUEST*2)/3); +/* find an empty request */ + while (--req >= request) + if (req->dev<0) + break; +/* if none found, sleep on new requests: check for rw_ahead */ + if (req < request) { + if (rw_ahead) { + unlock_buffer(bh); + return; + } + sleep_on(&wait_for_request); + goto repeat; + } +/* fill up the request-info, and add it to the queue */ + req->dev = bh->b_dev; + req->cmd = rw; + req->errors=0; + req->sector = bh->b_blocknr<<1; + req->nr_sectors = 2; + req->buffer = bh->b_data; + req->waiting = NULL; + req->bh = bh; + req->next = NULL; + add_request(major+blk_dev,req); +} + +void ll_rw_block(int rw, struct buffer_head * bh) +{ + unsigned int major; + + if ((major=MAJOR(bh->b_dev)) >= NR_BLK_DEV || + !(blk_dev[major].request_fn)) { + printk("Trying to read nonexistent block-device\n\r"); + return; + } + make_request(major,rw,bh); +} + +void blk_dev_init(void) +{ + int i; + + for (i=0 ; i