minix/lib/libminixfs/cache.c
David van Moolenbroek b48542d914 VM: readd support for forgetting cached FS blocks
Not all services involved in block I/O go through VM to access the
blocks they need.  As a result, the blocks in VM may become stale,
possibly causing corruption when the stale copy is restored by a
service that does go through VM later on.  This patch restores support
for forgetting cached blocks that belong to a particular device, and
makes the relevant file systems use this functionality 1) when
requested by VFS through REQ_FLUSH, and 2) upon unmount.

Change-Id: I0758c5ed8fe4b5ba81d432595d2113175776aff8
2014-03-01 09:04:53 +01:00

973 lines
25 KiB
C

#define _SYSTEM
#include <assert.h>
#include <errno.h>
#include <math.h>
#include <stdlib.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <minix/dmap.h>
#include <minix/libminixfs.h>
#include <minix/syslib.h>
#include <minix/sysutil.h>
#include <minix/u64.h>
#include <minix/bdev.h>
#define BUFHASH(b) ((b) % nr_bufs)
#define MARKCLEAN lmfs_markclean
#define MINBUFS 6 /* minimal no of bufs for sanity check */
static struct buf *front; /* points to least recently used free block */
static struct buf *rear; /* points to most recently used free block */
static unsigned int bufs_in_use;/* # bufs currently in use (not on free list)*/
static void rm_lru(struct buf *bp);
static void read_block(struct buf *);
static void flushall(dev_t dev);
static void freeblock(struct buf *bp);
static void cache_heuristic_check(int major);
static int vmcache = 0; /* are we using vm's secondary cache? (initially not) */
static struct buf *buf;
static struct buf **buf_hash; /* the buffer hash table */
static unsigned int nr_bufs;
static int may_use_vmcache;
static int fs_block_size = PAGE_SIZE; /* raw i/o block size */
static int rdwt_err;
static int quiet = 0;
void
lmfs_setquiet(int q) { quiet = q; }
static u32_t fs_bufs_heuristic(int minbufs, u32_t btotal, u64_t bfree,
int blocksize, dev_t majordev)
{
struct vm_stats_info vsi;
int bufs;
u32_t kbytes_used_fs, kbytes_total_fs, kbcache, kb_fsmax;
u32_t kbytes_remain_mem;
u64_t bused;
bused = btotal-bfree;
/* set a reasonable cache size; cache at most a certain
* portion of the used FS, and at most a certain %age of remaining
* memory
*/
if(vm_info_stats(&vsi) != OK) {
bufs = 1024;
if(!quiet)
printf("fslib: heuristic info fail: default to %d bufs\n", bufs);
return bufs;
}
/* remaining free memory is unused memory plus memory in used for cache,
* as the cache can be evicted
*/
kbytes_remain_mem = (u64_t)(vsi.vsi_free + vsi.vsi_cached) *
vsi.vsi_pagesize / 1024;
/* check fs usage. */
kbytes_used_fs = div64u(mul64u(bused, blocksize), 1024);
kbytes_total_fs = div64u(mul64u(btotal, blocksize), 1024);
/* heuristic for a desired cache size based on FS usage;
* but never bigger than half of the total filesystem
*/
kb_fsmax = sqrt_approx(kbytes_used_fs)*40;
kb_fsmax = MIN(kb_fsmax, kbytes_total_fs/2);
/* heuristic for a maximum usage - 10% of remaining memory */
kbcache = MIN(kbytes_remain_mem/10, kb_fsmax);
bufs = kbcache * 1024 / blocksize;
/* but we simply need MINBUFS no matter what */
if(bufs < minbufs)
bufs = minbufs;
return bufs;
}
void lmfs_blockschange(dev_t dev, int delta)
{
/* Change the number of allocated blocks by 'delta.'
* Also accumulate the delta since the last cache re-evaluation.
* If it is outside a certain band, ask the cache library to
* re-evaluate the cache size.
*/
static int bitdelta = 0;
bitdelta += delta;
#define BANDKB (10*1024) /* recheck cache every 10MB change */
if(bitdelta*fs_block_size/1024 > BANDKB ||
bitdelta*fs_block_size/1024 < -BANDKB) {
lmfs_cache_reevaluate(dev);
bitdelta = 0;
}
}
void
lmfs_markdirty(struct buf *bp)
{
bp->lmfs_flags |= VMMC_DIRTY;
}
void
lmfs_markclean(struct buf *bp)
{
bp->lmfs_flags &= ~VMMC_DIRTY;
}
int
lmfs_isclean(struct buf *bp)
{
return !(bp->lmfs_flags & VMMC_DIRTY);
}
dev_t
lmfs_dev(struct buf *bp)
{
return bp->lmfs_dev;
}
int lmfs_bytes(struct buf *bp)
{
return bp->lmfs_bytes;
}
static void
free_unused_blocks(void)
{
struct buf *bp;
int freed = 0, bytes = 0;
printf("libminixfs: freeing; %d blocks in use\n", bufs_in_use);
for(bp = &buf[0]; bp < &buf[nr_bufs]; bp++) {
if(bp->lmfs_bytes > 0 && bp->lmfs_count == 0) {
freed++;
bytes += bp->lmfs_bytes;
freeblock(bp);
}
}
printf("libminixfs: freeing; %d blocks, %d bytes\n", freed, bytes);
}
static void
lmfs_alloc_block(struct buf *bp)
{
int len;
ASSERT(!bp->data);
ASSERT(bp->lmfs_bytes == 0);
len = roundup(fs_block_size, PAGE_SIZE);
if((bp->data = minix_mmap(0, fs_block_size,
PROT_READ|PROT_WRITE, MAP_PREALLOC|MAP_ANON, -1, 0)) == MAP_FAILED) {
free_unused_blocks();
if((bp->data = minix_mmap(0, fs_block_size, PROT_READ|PROT_WRITE,
MAP_PREALLOC|MAP_ANON, -1, 0)) == MAP_FAILED) {
panic("libminixfs: could not allocate block");
}
}
assert(bp->data);
bp->lmfs_bytes = fs_block_size;
bp->lmfs_needsetcache = 1;
}
/*===========================================================================*
* lmfs_get_block *
*===========================================================================*/
struct buf *lmfs_get_block(register dev_t dev, register block_t block,
int only_search)
{
return lmfs_get_block_ino(dev, block, only_search, VMC_NO_INODE, 0);
}
void minix_munmap_t(void *a, int len)
{
vir_bytes av = (vir_bytes) a;
assert(a);
assert(a != MAP_FAILED);
assert(len > 0);
assert(!(av % PAGE_SIZE));
len = roundup(len, PAGE_SIZE);
assert(!(len % PAGE_SIZE));
if(minix_munmap(a, len) < 0)
panic("libminixfs cache: munmap failed");
}
static void raisecount(struct buf *bp)
{
assert(bufs_in_use >= 0);
ASSERT(bp->lmfs_count >= 0);
bp->lmfs_count++;
if(bp->lmfs_count == 1) bufs_in_use++;
assert(bufs_in_use > 0);
}
static void lowercount(struct buf *bp)
{
assert(bufs_in_use > 0);
ASSERT(bp->lmfs_count > 0);
bp->lmfs_count--;
if(bp->lmfs_count == 0) bufs_in_use--;
assert(bufs_in_use >= 0);
}
static void freeblock(struct buf *bp)
{
ASSERT(bp->lmfs_count == 0);
/* 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->lmfs_dev != NO_DEV) {
if (!lmfs_isclean(bp)) flushall(bp->lmfs_dev);
assert(bp->lmfs_bytes == fs_block_size);
bp->lmfs_dev = NO_DEV;
}
/* Fill in block's parameters and add it to the hash chain where it goes. */
MARKCLEAN(bp); /* NO_DEV blocks may be marked dirty */
if(bp->lmfs_bytes > 0) {
assert(bp->data);
minix_munmap_t(bp->data, bp->lmfs_bytes);
bp->lmfs_bytes = 0;
bp->data = NULL;
} else assert(!bp->data);
}
/*===========================================================================*
* lmfs_get_block_ino *
*===========================================================================*/
struct buf *lmfs_get_block_ino(dev_t dev, block_t block, int only_search,
ino_t ino, u64_t ino_off)
{
/* 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;
static struct buf *bp;
u64_t dev_off = (u64_t) block * fs_block_size;
struct buf *prev_ptr;
assert(buf_hash);
assert(buf);
assert(nr_bufs > 0);
ASSERT(fs_block_size > 0);
assert(dev != NO_DEV);
if((ino_off % fs_block_size)) {
printf("cache: unaligned lmfs_get_block_ino ino_off %llu\n",
ino_off);
util_stacktrace();
}
/* Search the hash chain for (dev, block). */
b = BUFHASH(block);
bp = buf_hash[b];
while (bp != NULL) {
if (bp->lmfs_blocknr == block && bp->lmfs_dev == dev) {
if(bp->lmfs_flags & VMMC_EVICTED) {
/* We had it but VM evicted it; invalidate it. */
ASSERT(bp->lmfs_count == 0);
ASSERT(!(bp->lmfs_flags & VMMC_BLOCK_LOCKED));
ASSERT(!(bp->lmfs_flags & VMMC_DIRTY));
bp->lmfs_dev = NO_DEV;
bp->lmfs_bytes = 0;
bp->data = NULL;
break;
}
ASSERT(bp->lmfs_needsetcache == 0);
/* Block needed has been found. */
if (bp->lmfs_count == 0) {
rm_lru(bp);
ASSERT(!(bp->lmfs_flags & VMMC_BLOCK_LOCKED));
bp->lmfs_flags |= VMMC_BLOCK_LOCKED;
}
raisecount(bp);
ASSERT(bp->lmfs_bytes == fs_block_size);
ASSERT(bp->lmfs_dev == dev);
ASSERT(bp->lmfs_dev != NO_DEV);
ASSERT(bp->lmfs_flags & VMMC_BLOCK_LOCKED);
ASSERT(bp->data);
if(ino != VMC_NO_INODE) {
if(bp->lmfs_inode == VMC_NO_INODE
|| bp->lmfs_inode != ino
|| bp->lmfs_inode_offset != ino_off) {
bp->lmfs_inode = ino;
bp->lmfs_inode_offset = ino_off;
bp->lmfs_needsetcache = 1;
}
}
return(bp);
} else {
/* This block is not the one sought. */
bp = bp->lmfs_hash; /* move to next block on hash chain */
}
}
/* Desired block is not on available chain. Find a free block to use. */
if(bp) {
ASSERT(bp->lmfs_flags & VMMC_EVICTED);
} else {
if ((bp = front) == NULL) panic("all buffers in use: %d", nr_bufs);
}
assert(bp);
rm_lru(bp);
/* Remove the block that was just taken from its hash chain. */
b = BUFHASH(bp->lmfs_blocknr);
prev_ptr = buf_hash[b];
if (prev_ptr == bp) {
buf_hash[b] = bp->lmfs_hash;
} else {
/* The block just taken is not on the front of its hash chain. */
while (prev_ptr->lmfs_hash != NULL)
if (prev_ptr->lmfs_hash == bp) {
prev_ptr->lmfs_hash = bp->lmfs_hash; /* found it */
break;
} else {
prev_ptr = prev_ptr->lmfs_hash; /* keep looking */
}
}
freeblock(bp);
bp->lmfs_inode = ino;
bp->lmfs_inode_offset = ino_off;
bp->lmfs_flags = VMMC_BLOCK_LOCKED;
bp->lmfs_needsetcache = 0;
bp->lmfs_dev = dev; /* fill in device number */
bp->lmfs_blocknr = block; /* fill in block number */
ASSERT(bp->lmfs_count == 0);
raisecount(bp);
b = BUFHASH(bp->lmfs_blocknr);
bp->lmfs_hash = buf_hash[b];
buf_hash[b] = bp; /* add to hash list */
assert(dev != NO_DEV);
/* Block is not found in our cache, but we do want it
* if it's in the vm cache.
*/
assert(!bp->data);
assert(!bp->lmfs_bytes);
if(vmcache) {
if((bp->data = vm_map_cacheblock(dev, dev_off, ino, ino_off,
&bp->lmfs_flags, fs_block_size)) != MAP_FAILED) {
bp->lmfs_bytes = fs_block_size;
ASSERT(!bp->lmfs_needsetcache);
return bp;
}
}
bp->data = NULL;
/* Not in the cache; reserve memory for its contents. */
lmfs_alloc_block(bp);
assert(bp->data);
if(only_search == PREFETCH) {
/* PREFETCH: don't do i/o. */
bp->lmfs_dev = NO_DEV;
} else if (only_search == NORMAL) {
read_block(bp);
} else if(only_search == NO_READ) {
/* This block will be overwritten by new contents. */
} else
panic("unexpected only_search value: %d", only_search);
assert(bp->data);
return(bp); /* return the newly acquired block */
}
/*===========================================================================*
* lmfs_put_block *
*===========================================================================*/
void lmfs_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.
*/
dev_t dev;
u64_t dev_off;
int r;
if (bp == NULL) return; /* it is easier to check here than in caller */
dev = bp->lmfs_dev;
dev_off = (u64_t) bp->lmfs_blocknr * fs_block_size;
lowercount(bp);
if (bp->lmfs_count != 0) return; /* block is still in use */
/* Put this block back on the LRU chain. */
if (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->lmfs_prev = NULL;
bp->lmfs_next = front;
if (front == NULL)
rear = bp; /* LRU chain was empty */
else
front->lmfs_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->lmfs_prev = rear;
bp->lmfs_next = NULL;
if (rear == NULL)
front = bp;
else
rear->lmfs_next = bp;
rear = bp;
}
assert(bp->lmfs_flags & VMMC_BLOCK_LOCKED);
bp->lmfs_flags &= ~VMMC_BLOCK_LOCKED;
/* block has sensible content - if necesary, identify it to VM */
if(vmcache && bp->lmfs_needsetcache && dev != NO_DEV) {
if((r=vm_set_cacheblock(bp->data, dev, dev_off,
bp->lmfs_inode, bp->lmfs_inode_offset,
&bp->lmfs_flags, fs_block_size)) != OK) {
if(r == ENOSYS) {
printf("libminixfs: ENOSYS, disabling VM calls\n");
vmcache = 0;
} else {
panic("libminixfs: setblock of %p dev 0x%x off "
"0x%llx failed\n", bp->data, dev, dev_off);
}
}
}
bp->lmfs_needsetcache = 0;
}
void lmfs_cache_reevaluate(dev_t dev)
{
if(bufs_in_use == 0 && dev != NO_DEV) {
/* if the cache isn't in use any more, we could resize it. */
cache_heuristic_check(major(dev));
}
}
/*===========================================================================*
* read_block *
*===========================================================================*/
static void read_block(bp)
register struct buf *bp; /* buffer pointer */
{
/* 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_failed;
u64_t pos;
dev_t dev = bp->lmfs_dev;
op_failed = 0;
assert(dev != NO_DEV);
ASSERT(bp->lmfs_bytes == fs_block_size);
ASSERT(fs_block_size > 0);
pos = mul64u(bp->lmfs_blocknr, fs_block_size);
if(fs_block_size > PAGE_SIZE) {
#define MAXPAGES 20
vir_bytes blockrem, vaddr = (vir_bytes) bp->data;
int p = 0;
static iovec_t iovec[MAXPAGES];
blockrem = fs_block_size;
while(blockrem > 0) {
vir_bytes chunk = blockrem >= PAGE_SIZE ? PAGE_SIZE : blockrem;
iovec[p].iov_addr = vaddr;
iovec[p].iov_size = chunk;
vaddr += chunk;
blockrem -= chunk;
p++;
}
r = bdev_gather(dev, pos, iovec, p, BDEV_NOFLAGS);
} else {
r = bdev_read(dev, pos, bp->data, fs_block_size,
BDEV_NOFLAGS);
}
if (r < 0) {
printf("fs cache: I/O error on device %d/%d, block %u\n",
major(dev), minor(dev), bp->lmfs_blocknr);
op_failed = 1;
} else if (r != (ssize_t) fs_block_size) {
r = END_OF_FILE;
op_failed = 1;
}
if (op_failed) {
bp->lmfs_dev = NO_DEV; /* invalidate block */
/* Report read errors to interested parties. */
rdwt_err = r;
}
}
/*===========================================================================*
* lmfs_invalidate *
*===========================================================================*/
void lmfs_invalidate(
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->lmfs_dev == device) {
assert(bp->data);
assert(bp->lmfs_bytes > 0);
minix_munmap_t(bp->data, bp->lmfs_bytes);
bp->lmfs_dev = NO_DEV;
bp->lmfs_bytes = 0;
bp->data = NULL;
}
}
vm_clear_cache(device);
}
/*===========================================================================*
* flushall *
*===========================================================================*/
static void flushall(dev_t dev)
{
/* Flush all dirty blocks for one device. */
register struct buf *bp;
static struct buf **dirty; /* static so it isn't on stack */
static unsigned int dirtylistsize = 0;
int ndirty;
if(dirtylistsize != nr_bufs) {
if(dirtylistsize > 0) {
assert(dirty != NULL);
free(dirty);
}
if(!(dirty = malloc(sizeof(dirty[0])*nr_bufs)))
panic("couldn't allocate dirty buf list");
dirtylistsize = nr_bufs;
}
for (bp = &buf[0], ndirty = 0; bp < &buf[nr_bufs]; bp++) {
if (!lmfs_isclean(bp) && bp->lmfs_dev == dev) {
dirty[ndirty++] = bp;
}
}
lmfs_rw_scattered(dev, dirty, ndirty, WRITING);
}
/*===========================================================================*
* lmfs_rw_scattered *
*===========================================================================*/
void lmfs_rw_scattered(
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];
u64_t pos;
int iov_per_block;
int start_in_use = bufs_in_use, start_bufqsize = bufqsize;
assert(bufqsize >= 0);
if(bufqsize == 0) return;
/* for READING, check all buffers on the list are obtained and held
* (count > 0)
*/
if (rw_flag == READING) {
for(i = 0; i < bufqsize; i++) {
assert(bufq[i] != NULL);
assert(bufq[i]->lmfs_count > 0);
}
/* therefore they are all 'in use' and must be at least this many */
assert(start_in_use >= start_bufqsize);
}
assert(dev != NO_DEV);
assert(fs_block_size > 0);
iov_per_block = roundup(fs_block_size, PAGE_SIZE) / PAGE_SIZE;
assert(iov_per_block < NR_IOREQS);
/* (Shell) sort buffers on lmfs_blocknr. */
gap = 1;
do
gap = 3 * gap + 1;
while (gap <= bufqsize);
while (gap != 1) {
int j;
gap /= 3;
for (j = gap; j < bufqsize; j++) {
for (i = j - gap;
i >= 0 && bufq[i]->lmfs_blocknr > bufq[i + gap]->lmfs_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 bdev I/O is OK if everything
* went fine, otherwise the error code for the first failed transfer.
*/
while (bufqsize > 0) {
int nblocks = 0, niovecs = 0;
int r;
for (iop = iovec; nblocks < bufqsize; nblocks++) {
int p;
vir_bytes vdata, blockrem;
bp = bufq[nblocks];
if (bp->lmfs_blocknr != (block_t) bufq[0]->lmfs_blocknr + nblocks)
break;
if(niovecs >= NR_IOREQS-iov_per_block) break;
vdata = (vir_bytes) bp->data;
blockrem = fs_block_size;
for(p = 0; p < iov_per_block; p++) {
vir_bytes chunk = blockrem < PAGE_SIZE ? blockrem : PAGE_SIZE;
iop->iov_addr = vdata;
iop->iov_size = chunk;
vdata += PAGE_SIZE;
blockrem -= chunk;
iop++;
niovecs++;
}
assert(p == iov_per_block);
assert(blockrem == 0);
}
assert(nblocks > 0);
assert(niovecs > 0);
pos = mul64u(bufq[0]->lmfs_blocknr, fs_block_size);
if (rw_flag == READING)
r = bdev_gather(dev, pos, iovec, niovecs, BDEV_NOFLAGS);
else
r = bdev_scatter(dev, pos, iovec, niovecs, BDEV_NOFLAGS);
/* Harvest the results. The driver may have returned an error, or it
* may have done less than what we asked for.
*/
if (r < 0) {
printf("fs cache: I/O error %d on device %d/%d, block %u\n",
r, major(dev), minor(dev), bufq[0]->lmfs_blocknr);
}
for (i = 0; i < nblocks; i++) {
bp = bufq[i];
if (r < (ssize_t) fs_block_size) {
/* Transfer failed. */
if (i == 0) {
bp->lmfs_dev = NO_DEV; /* Invalidate block */
}
break;
}
if (rw_flag == READING) {
bp->lmfs_dev = dev; /* validate block */
lmfs_put_block(bp, PARTIAL_DATA_BLOCK);
} else {
MARKCLEAN(bp);
}
r -= fs_block_size;
}
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) {
lmfs_put_block(*bufq++, PARTIAL_DATA_BLOCK);
bufqsize--;
}
}
if (rw_flag == WRITING && i == 0) {
/* We're not making progress, this means we might keep
* looping. Buffers remain dirty if un-written. Buffers are
* lost if invalidate()d or LRU-removed while dirty. This
* is better than keeping unwritable blocks around forever..
*/
break;
}
}
if(rw_flag == READING) {
assert(start_in_use >= start_bufqsize);
/* READING callers assume all bufs are released. */
assert(start_in_use - start_bufqsize == bufs_in_use);
}
}
/*===========================================================================*
* rm_lru *
*===========================================================================*/
static void rm_lru(bp)
struct buf *bp;
{
/* Remove a block from its LRU chain. */
struct buf *next_ptr, *prev_ptr;
next_ptr = bp->lmfs_next; /* successor on LRU chain */
prev_ptr = bp->lmfs_prev; /* predecessor on LRU chain */
if (prev_ptr != NULL)
prev_ptr->lmfs_next = next_ptr;
else
front = next_ptr; /* this block was at front of chain */
if (next_ptr != NULL)
next_ptr->lmfs_prev = prev_ptr;
else
rear = prev_ptr; /* this block was at rear of chain */
}
/*===========================================================================*
* cache_resize *
*===========================================================================*/
static void cache_resize(unsigned int blocksize, unsigned int bufs)
{
struct buf *bp;
assert(blocksize > 0);
assert(bufs >= MINBUFS);
for (bp = &buf[0]; bp < &buf[nr_bufs]; bp++)
if(bp->lmfs_count != 0) panic("change blocksize with buffer in use");
lmfs_buf_pool(bufs);
fs_block_size = blocksize;
}
static void cache_heuristic_check(int major)
{
int bufs, d;
u64_t btotal, bfree, bused;
fs_blockstats(&btotal, &bfree, &bused);
bufs = fs_bufs_heuristic(10, btotal, bfree,
fs_block_size, major);
/* set the cache to the new heuristic size if the new one
* is more than 10% off from the current one.
*/
d = bufs-nr_bufs;
if(d < 0) d = -d;
if(d*100/nr_bufs > 10) {
cache_resize(fs_block_size, bufs);
}
}
/*===========================================================================*
* lmfs_set_blocksize *
*===========================================================================*/
void lmfs_set_blocksize(int new_block_size, int major)
{
cache_resize(new_block_size, MINBUFS);
cache_heuristic_check(major);
/* Decide whether to use seconday cache or not.
* Only do this if
* - it's available, and
* - use of it hasn't been disabled for this fs, and
* - our main FS device isn't a memory device
*/
vmcache = 0;
if(may_use_vmcache && !(new_block_size % PAGE_SIZE))
vmcache = 1;
}
/*===========================================================================*
* lmfs_buf_pool *
*===========================================================================*/
void lmfs_buf_pool(int new_nr_bufs)
{
/* Initialize the buffer pool. */
register struct buf *bp;
assert(new_nr_bufs >= MINBUFS);
if(nr_bufs > 0) {
assert(buf);
(void) fs_sync();
for (bp = &buf[0]; bp < &buf[nr_bufs]; bp++) {
if(bp->data) {
assert(bp->lmfs_bytes > 0);
minix_munmap_t(bp->data, bp->lmfs_bytes);
}
}
}
if(buf)
free(buf);
if(!(buf = calloc(sizeof(buf[0]), new_nr_bufs)))
panic("couldn't allocate buf list (%d)", new_nr_bufs);
if(buf_hash)
free(buf_hash);
if(!(buf_hash = calloc(sizeof(buf_hash[0]), new_nr_bufs)))
panic("couldn't allocate buf hash list (%d)", new_nr_bufs);
nr_bufs = new_nr_bufs;
bufs_in_use = 0;
front = &buf[0];
rear = &buf[nr_bufs - 1];
for (bp = &buf[0]; bp < &buf[nr_bufs]; bp++) {
bp->lmfs_blocknr = NO_BLOCK;
bp->lmfs_dev = NO_DEV;
bp->lmfs_next = bp + 1;
bp->lmfs_prev = bp - 1;
bp->data = NULL;
bp->lmfs_bytes = 0;
}
front->lmfs_prev = NULL;
rear->lmfs_next = NULL;
for (bp = &buf[0]; bp < &buf[nr_bufs]; bp++) bp->lmfs_hash = bp->lmfs_next;
buf_hash[0] = front;
}
int lmfs_bufs_in_use(void)
{
return bufs_in_use;
}
int lmfs_nr_bufs(void)
{
return nr_bufs;
}
void lmfs_flushall(void)
{
struct buf *bp;
for(bp = &buf[0]; bp < &buf[nr_bufs]; bp++)
if(bp->lmfs_dev != NO_DEV && !lmfs_isclean(bp))
flushall(bp->lmfs_dev);
}
int lmfs_fs_block_size(void)
{
return fs_block_size;
}
void lmfs_may_use_vmcache(int ok)
{
may_use_vmcache = ok;
}
void lmfs_reset_rdwt_err(void)
{
rdwt_err = OK;
}
int lmfs_rdwt_err(void)
{
return rdwt_err;
}
int lmfs_do_bpeek(message *m)
{
block_t startblock, b, limitblock;
dev_t dev = m->REQ_DEV2;
u64_t extra, pos = make64(m->REQ_SEEK_POS_LO, m->REQ_SEEK_POS_HI);
size_t len = m->REQ_NBYTES;
struct buf *bp;
assert(m->m_type == REQ_BPEEK);
assert(fs_block_size > 0);
assert(dev != NO_DEV);
if(!vmcache) { return ENXIO; }
assert(!(fs_block_size % PAGE_SIZE));
if((extra=(pos % fs_block_size))) {
pos -= extra;
len += extra;
}
len = roundup(len, fs_block_size);
startblock = pos/fs_block_size;
limitblock = startblock + len/fs_block_size;
for(b = startblock; b < limitblock; b++) {
bp = lmfs_get_block(dev, b, NORMAL);
assert(bp);
lmfs_put_block(bp, FULL_DATA_BLOCK);
}
return OK;
}