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mfs: improve & simplify secondary cache logic

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. fixes "!" errors when booting from cd
This commit is contained in:
Ben Gras 2011-09-21 17:52:45 +00:00
parent 05341dfeb0
commit 49532259e5
2 changed files with 15 additions and 18 deletions
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31
servers/mfs/cache.c
View file

@ -28,7 +28,7 @@
FORWARD _PROTOTYPE( void rm_lru, (struct buf *bp) );
FORWARD _PROTOTYPE( void rw_block, (struct buf *, int) );
PRIVATE int vmcache_avail = -1; /* 0 if not available, >0 if available. */
PRIVATE int vmcache = 0; /* are we using vm's secondary cache? (initially not) */
/*===========================================================================*
* get_block *
@ -57,27 +57,11 @@ PUBLIC struct buf *get_block(
int b;
static struct buf *bp, *prev_ptr;
u64_t yieldid = VM_BLOCKID_NONE, getid = make64(dev, block);
int vmcache = 0;
assert(buf_hash);
assert(buf);
assert(nr_bufs > 0);
if(vmcache_avail < 0) {
/* Test once for the availability of the vm yield block feature. */
if(vm_forgetblock(VM_BLOCKID_NONE) == ENOSYS) {
vmcache_avail = 0;
} else {
vmcache_avail = 1;
}
}
/* use vmcache if it's available, and allowed, and we're not doing
* i/o on a ram disk device.
*/
if(vmcache_avail && may_use_vmcache && major(dev) != MEMORY_MAJOR)
vmcache = 1;
ASSERT(fs_block_size > 0);
/* Search the hash chain for (dev, block). Do_read() can use
@ -586,6 +570,19 @@ PUBLIC void set_blocksize(struct super_block *sp)
cache_resize(sp->s_block_size, MINBUFS);
bufs = bufs_heuristic(sp);
cache_resize(sp->s_block_size, bufs);
/* 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(vm_forgetblock(VM_BLOCKID_NONE) != ENOSYS &&
may_use_vmcache && major(sp->s_dev) != MEMORY_MAJOR) {
vmcache = 1;
}
}
/*===========================================================================*

2
servers/mfs/read.c
View file

@ -412,7 +412,7 @@ PUBLIC void read_ahead()
rdahed_inode = NULL; /* turn off read ahead */
if ( (b = read_map(rip, rdahedpos)) == NO_BLOCK) return; /* at EOF */
assert(rdahedpos > 0); /* So we can safely cast it to unsigned below */
assert(rdahedpos >= 0); /* So we can safely cast it to unsigned below */
bp = rahead(rip, b, cvul64( (unsigned long) rdahedpos), block_size);
put_block(bp, PARTIAL_DATA_BLOCK);