6d23f072f3
names. All system processes can now either use panic() or report() from libutils, or redefine their own function. Assertions are done via the standard <assert.h> functionality.
435 lines
14 KiB
C
435 lines
14 KiB
C
/* The file system maintains a buffer cache to reduce the number of disk
|
|
* accesses needed. Whenever a read or write to the disk is done, a check is
|
|
* first made to see if the block is in the cache. This file manages the
|
|
* cache.
|
|
*
|
|
* The entry points into this file are:
|
|
* get_block: request to fetch a block for reading or writing from cache
|
|
* put_block: return a block previously requested with get_block
|
|
* alloc_zone: allocate a new zone (to increase the length of a file)
|
|
* free_zone: release a zone (when a file is removed)
|
|
* rw_block: read or write a block from the disk itself
|
|
* invalidate: remove all the cache blocks on some device
|
|
*/
|
|
|
|
#include "fs.h"
|
|
#include <minix/com.h>
|
|
#include "buf.h"
|
|
#include "file.h"
|
|
#include "fproc.h"
|
|
#include "super.h"
|
|
|
|
FORWARD _PROTOTYPE( void rm_lru, (struct buf *bp) );
|
|
|
|
/*===========================================================================*
|
|
* get_block *
|
|
*===========================================================================*/
|
|
PUBLIC struct buf *get_block(dev, block, only_search)
|
|
register dev_t dev; /* on which device is the block? */
|
|
register block_t block; /* which block is wanted? */
|
|
int only_search; /* if NO_READ, don't read, else act normal */
|
|
{
|
|
/* Check to see if the requested block is in the block cache. If so, return
|
|
* a pointer to it. If not, evict some other block and fetch it (unless
|
|
* 'only_search' is 1). All the blocks in the cache that are not in use
|
|
* are linked together in a chain, with 'front' pointing to the least recently
|
|
* used block and 'rear' to the most recently used block. If 'only_search' is
|
|
* 1, the block being requested will be overwritten in its entirety, so it is
|
|
* only necessary to see if it is in the cache; if it is not, any free buffer
|
|
* will do. It is not necessary to actually read the block in from disk.
|
|
* If 'only_search' is PREFETCH, the block need not be read from the disk,
|
|
* and the device is not to be marked on the block, so callers can tell if
|
|
* the block returned is valid.
|
|
* In addition to the LRU chain, there is also a hash chain to link together
|
|
* blocks whose block numbers end with the same bit strings, for fast lookup.
|
|
*/
|
|
|
|
int b;
|
|
register struct buf *bp, *prev_ptr;
|
|
|
|
/* Search the hash chain for (dev, block). Do_read() can use
|
|
* get_block(NO_DEV ...) to get an unnamed block to fill with zeros when
|
|
* someone wants to read from a hole in a file, in which case this search
|
|
* is skipped
|
|
*/
|
|
if (dev != NO_DEV) {
|
|
b = (int) block & HASH_MASK;
|
|
bp = buf_hash[b];
|
|
while (bp != NIL_BUF) {
|
|
if (bp->b_blocknr == block && bp->b_dev == dev) {
|
|
/* Block needed has been found. */
|
|
if (bp->b_count == 0) rm_lru(bp);
|
|
bp->b_count++; /* record that block is in use */
|
|
return(bp);
|
|
} else {
|
|
/* This block is not the one sought. */
|
|
bp = bp->b_hash; /* move to next block on hash chain */
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Desired block is not on available chain. Take oldest block ('front'). */
|
|
if ((bp = front) == NIL_BUF) panic(__FILE__,"all buffers in use", NR_BUFS);
|
|
rm_lru(bp);
|
|
|
|
/* Remove the block that was just taken from its hash chain. */
|
|
b = (int) bp->b_blocknr & HASH_MASK;
|
|
prev_ptr = buf_hash[b];
|
|
if (prev_ptr == bp) {
|
|
buf_hash[b] = bp->b_hash;
|
|
} else {
|
|
/* The block just taken is not on the front of its hash chain. */
|
|
while (prev_ptr->b_hash != NIL_BUF)
|
|
if (prev_ptr->b_hash == bp) {
|
|
prev_ptr->b_hash = bp->b_hash; /* found it */
|
|
break;
|
|
} else {
|
|
prev_ptr = prev_ptr->b_hash; /* keep looking */
|
|
}
|
|
}
|
|
|
|
/* If the block taken is dirty, make it clean by writing it to the disk.
|
|
* Avoid hysteresis by flushing all other dirty blocks for the same device.
|
|
*/
|
|
if (bp->b_dev != NO_DEV) {
|
|
if (bp->b_dirt == DIRTY) flushall(bp->b_dev);
|
|
#if ENABLE_CACHE2
|
|
put_block2(bp);
|
|
#endif
|
|
}
|
|
|
|
/* Fill in block's parameters and add it to the hash chain where it goes. */
|
|
bp->b_dev = dev; /* fill in device number */
|
|
bp->b_blocknr = block; /* fill in block number */
|
|
bp->b_count++; /* record that block is being used */
|
|
b = (int) bp->b_blocknr & HASH_MASK;
|
|
bp->b_hash = buf_hash[b];
|
|
buf_hash[b] = bp; /* add to hash list */
|
|
|
|
/* Go get the requested block unless searching or prefetching. */
|
|
if (dev != NO_DEV) {
|
|
#if ENABLE_CACHE2
|
|
if (get_block2(bp, only_search)) /* in 2nd level cache */;
|
|
else
|
|
#endif
|
|
if (only_search == PREFETCH) bp->b_dev = NO_DEV;
|
|
else
|
|
if (only_search == NORMAL) rw_block(bp, READING);
|
|
}
|
|
return(bp); /* return the newly acquired block */
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* put_block *
|
|
*===========================================================================*/
|
|
PUBLIC void put_block(bp, block_type)
|
|
register struct buf *bp; /* pointer to the buffer to be released */
|
|
int block_type; /* INODE_BLOCK, DIRECTORY_BLOCK, or whatever */
|
|
{
|
|
/* Return a block to the list of available blocks. Depending on 'block_type'
|
|
* it may be put on the front or rear of the LRU chain. Blocks that are
|
|
* expected to be needed again shortly (e.g., partially full data blocks)
|
|
* go on the rear; blocks that are unlikely to be needed again shortly
|
|
* (e.g., full data blocks) go on the front. Blocks whose loss can hurt
|
|
* the integrity of the file system (e.g., inode blocks) are written to
|
|
* disk immediately if they are dirty.
|
|
*/
|
|
if (bp == NIL_BUF) return; /* it is easier to check here than in caller */
|
|
|
|
bp->b_count--; /* there is one use fewer now */
|
|
if (bp->b_count != 0) return; /* block is still in use */
|
|
|
|
bufs_in_use--; /* one fewer block buffers in use */
|
|
|
|
/* Put this block back on the LRU chain. If the ONE_SHOT bit is set in
|
|
* 'block_type', the block is not likely to be needed again shortly, so put
|
|
* it on the front of the LRU chain where it will be the first one to be
|
|
* taken when a free buffer is needed later.
|
|
*/
|
|
if (bp->b_dev == DEV_RAM || block_type & ONE_SHOT) {
|
|
/* Block probably won't be needed quickly. Put it on front of chain.
|
|
* It will be the next block to be evicted from the cache.
|
|
*/
|
|
bp->b_prev = NIL_BUF;
|
|
bp->b_next = front;
|
|
if (front == NIL_BUF)
|
|
rear = bp; /* LRU chain was empty */
|
|
else
|
|
front->b_prev = bp;
|
|
front = bp;
|
|
} else {
|
|
/* Block probably will be needed quickly. Put it on rear of chain.
|
|
* It will not be evicted from the cache for a long time.
|
|
*/
|
|
bp->b_prev = rear;
|
|
bp->b_next = NIL_BUF;
|
|
if (rear == NIL_BUF)
|
|
front = bp;
|
|
else
|
|
rear->b_next = bp;
|
|
rear = bp;
|
|
}
|
|
|
|
/* Some blocks are so important (e.g., inodes, indirect blocks) that they
|
|
* should be written to the disk immediately to avoid messing up the file
|
|
* system in the event of a crash.
|
|
*/
|
|
if ((block_type & WRITE_IMMED) && bp->b_dirt==DIRTY && bp->b_dev != NO_DEV)
|
|
rw_block(bp, WRITING);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* alloc_zone *
|
|
*===========================================================================*/
|
|
PUBLIC zone_t alloc_zone(dev, z)
|
|
dev_t dev; /* device where zone wanted */
|
|
zone_t z; /* try to allocate new zone near this one */
|
|
{
|
|
/* Allocate a new zone on the indicated device and return its number. */
|
|
|
|
int major, minor;
|
|
bit_t b, bit;
|
|
struct super_block *sp;
|
|
|
|
/* Note that the routine alloc_bit() returns 1 for the lowest possible
|
|
* zone, which corresponds to sp->s_firstdatazone. To convert a value
|
|
* between the bit number, 'b', used by alloc_bit() and the zone number, 'z',
|
|
* stored in the inode, use the formula:
|
|
* z = b + sp->s_firstdatazone - 1
|
|
* Alloc_bit() never returns 0, since this is used for NO_BIT (failure).
|
|
*/
|
|
sp = get_super(dev);
|
|
|
|
/* If z is 0, skip initial part of the map known to be fully in use. */
|
|
if (z == sp->s_firstdatazone) {
|
|
bit = sp->s_zsearch;
|
|
} else {
|
|
bit = (bit_t) z - (sp->s_firstdatazone - 1);
|
|
}
|
|
b = alloc_bit(sp, ZMAP, bit);
|
|
if (b == NO_BIT) {
|
|
err_code = ENOSPC;
|
|
major = (int) (sp->s_dev >> MAJOR) & BYTE;
|
|
minor = (int) (sp->s_dev >> MINOR) & BYTE;
|
|
printf("No space on %sdevice %d/%d\n",
|
|
sp->s_dev == root_dev ? "root " : "", major, minor);
|
|
return(NO_ZONE);
|
|
}
|
|
if (z == sp->s_firstdatazone) sp->s_zsearch = b; /* for next time */
|
|
return(sp->s_firstdatazone - 1 + (zone_t) b);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* free_zone *
|
|
*===========================================================================*/
|
|
PUBLIC void free_zone(dev, numb)
|
|
dev_t dev; /* device where zone located */
|
|
zone_t numb; /* zone to be returned */
|
|
{
|
|
/* Return a zone. */
|
|
|
|
register struct super_block *sp;
|
|
bit_t bit;
|
|
|
|
/* Locate the appropriate super_block and return bit. */
|
|
sp = get_super(dev);
|
|
if (numb < sp->s_firstdatazone || numb >= sp->s_zones) return;
|
|
bit = (bit_t) (numb - (sp->s_firstdatazone - 1));
|
|
free_bit(sp, ZMAP, bit);
|
|
if (bit < sp->s_zsearch) sp->s_zsearch = bit;
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* rw_block *
|
|
*===========================================================================*/
|
|
PUBLIC void rw_block(bp, rw_flag)
|
|
register struct buf *bp; /* buffer pointer */
|
|
int rw_flag; /* READING or WRITING */
|
|
{
|
|
/* Read or write a disk block. This is the only routine in which actual disk
|
|
* I/O is invoked. If an error occurs, a message is printed here, but the error
|
|
* is not reported to the caller. If the error occurred while purging a block
|
|
* from the cache, it is not clear what the caller could do about it anyway.
|
|
*/
|
|
|
|
int r, op;
|
|
off_t pos;
|
|
dev_t dev;
|
|
int block_size;
|
|
|
|
block_size = get_block_size(bp->b_dev);
|
|
|
|
if ( (dev = bp->b_dev) != NO_DEV) {
|
|
pos = (off_t) bp->b_blocknr * block_size;
|
|
op = (rw_flag == READING ? DEV_READ : DEV_WRITE);
|
|
r = dev_io(op, dev, FS_PROC_NR, bp->b_data, pos, block_size, 0);
|
|
if (r != block_size) {
|
|
if (r >= 0) r = END_OF_FILE;
|
|
if (r != END_OF_FILE)
|
|
printf("Unrecoverable disk error on device %d/%d, block %ld\n",
|
|
(dev>>MAJOR)&BYTE, (dev>>MINOR)&BYTE, bp->b_blocknr);
|
|
bp->b_dev = NO_DEV; /* invalidate block */
|
|
|
|
/* Report read errors to interested parties. */
|
|
if (rw_flag == READING) rdwt_err = r;
|
|
}
|
|
}
|
|
|
|
bp->b_dirt = CLEAN;
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* invalidate *
|
|
*===========================================================================*/
|
|
PUBLIC void invalidate(device)
|
|
dev_t device; /* device whose blocks are to be purged */
|
|
{
|
|
/* Remove all the blocks belonging to some device from the cache. */
|
|
|
|
register struct buf *bp;
|
|
|
|
for (bp = &buf[0]; bp < &buf[NR_BUFS]; bp++)
|
|
if (bp->b_dev == device) bp->b_dev = NO_DEV;
|
|
|
|
#if ENABLE_CACHE2
|
|
invalidate2(device);
|
|
#endif
|
|
}
|
|
|
|
|
|
/*==========================================================================*
|
|
* flushall *
|
|
*==========================================================================*/
|
|
PUBLIC void flushall(dev)
|
|
dev_t dev; /* device to flush */
|
|
{
|
|
/* Flush all dirty blocks for one device. */
|
|
|
|
register struct buf *bp;
|
|
static struct buf *dirty[NR_BUFS]; /* static so it isn't on stack */
|
|
int ndirty;
|
|
|
|
for (bp = &buf[0], ndirty = 0; bp < &buf[NR_BUFS]; bp++)
|
|
if (bp->b_dirt == DIRTY && bp->b_dev == dev) dirty[ndirty++] = bp;
|
|
rw_scattered(dev, dirty, ndirty, WRITING);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* rw_scattered *
|
|
*===========================================================================*/
|
|
PUBLIC void rw_scattered(dev, bufq, bufqsize, rw_flag)
|
|
dev_t dev; /* major-minor device number */
|
|
struct buf **bufq; /* pointer to array of buffers */
|
|
int bufqsize; /* number of buffers */
|
|
int rw_flag; /* READING or WRITING */
|
|
{
|
|
/* Read or write scattered data from a device. */
|
|
|
|
register struct buf *bp;
|
|
int gap;
|
|
register int i;
|
|
register iovec_t *iop;
|
|
static iovec_t iovec[NR_IOREQS]; /* static so it isn't on stack */
|
|
int j, r;
|
|
int block_size;
|
|
|
|
block_size = get_block_size(dev);
|
|
|
|
/* (Shell) sort buffers on b_blocknr. */
|
|
gap = 1;
|
|
do
|
|
gap = 3 * gap + 1;
|
|
while (gap <= bufqsize);
|
|
while (gap != 1) {
|
|
gap /= 3;
|
|
for (j = gap; j < bufqsize; j++) {
|
|
for (i = j - gap;
|
|
i >= 0 && bufq[i]->b_blocknr > bufq[i + gap]->b_blocknr;
|
|
i -= gap) {
|
|
bp = bufq[i];
|
|
bufq[i] = bufq[i + gap];
|
|
bufq[i + gap] = bp;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Set up I/O vector and do I/O. The result of dev_io is OK if everything
|
|
* went fine, otherwise the error code for the first failed transfer.
|
|
*/
|
|
while (bufqsize > 0) {
|
|
for (j = 0, iop = iovec; j < NR_IOREQS && j < bufqsize; j++, iop++) {
|
|
bp = bufq[j];
|
|
if (bp->b_blocknr != bufq[0]->b_blocknr + j) break;
|
|
iop->iov_addr = (vir_bytes) bp->b_data;
|
|
iop->iov_size = block_size;
|
|
}
|
|
r = dev_io(rw_flag == WRITING ? DEV_SCATTER : DEV_GATHER,
|
|
dev, FS_PROC_NR, iovec,
|
|
(off_t) bufq[0]->b_blocknr * block_size, j, 0);
|
|
|
|
/* Harvest the results. Dev_io reports the first error it may have
|
|
* encountered, but we only care if it's the first block that failed.
|
|
*/
|
|
for (i = 0, iop = iovec; i < j; i++, iop++) {
|
|
bp = bufq[i];
|
|
if (iop->iov_size != 0) {
|
|
/* Transfer failed. An error? Do we care? */
|
|
if (r != OK && i == 0) {
|
|
printf(
|
|
"fs: I/O error on device %d/%d, block %lu\n",
|
|
(dev>>MAJOR)&BYTE, (dev>>MINOR)&BYTE,
|
|
bp->b_blocknr);
|
|
bp->b_dev = NO_DEV; /* invalidate block */
|
|
}
|
|
break;
|
|
}
|
|
if (rw_flag == READING) {
|
|
bp->b_dev = dev; /* validate block */
|
|
put_block(bp, PARTIAL_DATA_BLOCK);
|
|
} else {
|
|
bp->b_dirt = CLEAN;
|
|
}
|
|
}
|
|
bufq += i;
|
|
bufqsize -= i;
|
|
if (rw_flag == READING) {
|
|
/* Don't bother reading more than the device is willing to
|
|
* give at this time. Don't forget to release those extras.
|
|
*/
|
|
while (bufqsize > 0) {
|
|
put_block(*bufq++, PARTIAL_DATA_BLOCK);
|
|
bufqsize--;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* rm_lru *
|
|
*===========================================================================*/
|
|
PRIVATE void rm_lru(bp)
|
|
struct buf *bp;
|
|
{
|
|
/* Remove a block from its LRU chain. */
|
|
struct buf *next_ptr, *prev_ptr;
|
|
|
|
bufs_in_use++;
|
|
next_ptr = bp->b_next; /* successor on LRU chain */
|
|
prev_ptr = bp->b_prev; /* predecessor on LRU chain */
|
|
if (prev_ptr != NIL_BUF)
|
|
prev_ptr->b_next = next_ptr;
|
|
else
|
|
front = next_ptr; /* this block was at front of chain */
|
|
|
|
if (next_ptr != NIL_BUF)
|
|
next_ptr->b_prev = prev_ptr;
|
|
else
|
|
rear = prev_ptr; /* this block was at rear of chain */
|
|
}
|