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ext2: No cache for you

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This commit is contained in:
K. Lange 2021-11-15 21:51:47 +09:00
parent f3759daadf
commit e5b35c1b47
1 changed files with 5 additions and 223 deletions
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222
modules/ext2.c
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@ -170,15 +170,6 @@ struct ext2_dir {
typedef struct ext2_dir ext2_dir_t;
typedef struct {
uint32_t block_no;
uint32_t last_use;
uint8_t dirty;
uint8_t *block;
} ext2_disk_cache_entry_t;
typedef int (*ext2_block_io_t) (void *, uint32_t, uint8_t *);
#define EXT2_BGD_BLOCK 2
#define E_SUCCESS 0
@ -204,12 +195,6 @@ typedef struct {
unsigned int inodes_per_group; /* Number of inodes in a "group" */
unsigned int block_group_count; /* Number of blocks groups */
ext2_disk_cache_entry_t * disk_cache; /* Dynamically allocated array of cache entries */
unsigned int cache_entries; /* Size of ->disk_cache */
unsigned int cache_time; /* "timer" that increments with each cache read/write */
spin_lock_t lock; /* Synchronization lock point */
uint8_t bgd_block_span;
uint8_t bgd_offset;
unsigned int inode_size;
@ -219,7 +204,6 @@ typedef struct {
int flags;
} ext2_fs_t;
#define EXT2_FLAG_NOCACHE 0x0001
#define EXT2_FLAG_READWRITE 0x0002
#define EXT2_FLAG_LOUD 0x0004
@ -231,7 +215,6 @@ typedef struct {
#define SB (this->superblock)
#define BGD (this->block_groups)
#define RN (this->root_node)
#define DC (this->disk_cache)
/*
* These macros deal with the block group descriptor bitmap
@ -248,52 +231,6 @@ static int write_inode(ext2_fs_t * this, ext2_inodetable_t *inode, size_t index)
static fs_node_t * finddir_ext2(fs_node_t *node, char *name);
static size_t allocate_block(ext2_fs_t * this);
static void yield_lock_acquire(spin_lock_t * lock) {
size_t spin_count = 0;
while (__sync_lock_test_and_set(lock->latch, 0x01)) {
if (spin_count == 10) {
unsigned long s, ss;
relative_time(0, 10, &s, &ss);
sleep_until((process_t *)this_core->current_process, s, ss);
switch_task(0);
spin_count = 0;
} else {
switch_task(1);
spin_count++;
}
}
lock->owner = this_core->cpu_id + 1;
lock->func = "yield_lock_acquire";
}
static void yield_lock_release(spin_lock_t * lock) {
lock->func = NULL;
lock->owner = -1;
__sync_lock_release(lock->latch);
}
/**
* ext2->get_cache_time Increment and return the current cache time
*
* @returns Current cache time
*/
static size_t get_cache_time(ext2_fs_t * this) {
return this->cache_time++;
}
/**
* ext2->cache_flush_dirty Flush dirty cache entry to the disk.
*
* @param ent_no Cache entry to dump
* @returns Error code or E_SUCCESS
*/
static int cache_flush_dirty(ext2_fs_t * this, size_t ent_no) {
write_fs(this->block_device, (DC[ent_no].block_no) * this->block_size, this->block_size, (uint8_t *)(DC[ent_no].block));
DC[ent_no].dirty = 0;
return E_SUCCESS;
}
/**
* ext2->rewrite_superblock Rewrite the superblock.
*
@ -321,71 +258,13 @@ static int read_block(ext2_fs_t * this, unsigned int block_no, uint8_t * buf) {
return E_BADBLOCK;
}
/* This operation requires the filesystem lock to be obtained */
yield_lock_acquire(&this->lock);
/* We can make reads without a cache in place. */
if (!DC) {
/* In such cases, we read directly from the block device */
read_fs(this->block_device, block_no * this->block_size, this->block_size, (uint8_t *)buf);
/* We are done, release the lock */
yield_lock_release(&this->lock);
/* And return SUCCESS */
return E_SUCCESS;
}
/*
* Search the cache for this entry
* We'll look for the oldest entry, too.
*/
int oldest = -1;
unsigned int oldest_age = UINT32_MAX;
for (unsigned int i = 0; i < this->cache_entries; ++i) {
if (DC[i].block_no == block_no) {
/* We found it! Update usage times */
DC[i].last_use = get_cache_time(this);
/* Read the block */
memcpy(buf, DC[i].block, this->block_size);
/* Release the lock */
yield_lock_release(&this->lock);
/* Success! */
return E_SUCCESS;
}
if (DC[i].last_use < oldest_age) {
/* We found an older block, remember this. */
oldest = i;
oldest_age = DC[i].last_use;
}
}
/*
* At this point, we did not find this block in the cache.
* We are going to replace the oldest entry with this new one.
*/
/* We'll start by flushing the block if it was dirty. */
if (DC[oldest].dirty) {
cache_flush_dirty(this, oldest);
}
/* Then we'll read the new one */
read_fs(this->block_device, block_no * this->block_size, this->block_size, (uint8_t *)DC[oldest].block);
/* And copy the results to the output buffer */
memcpy(buf, DC[oldest].block, this->block_size);
/* And update the cache entry to point to the new block */
DC[oldest].block_no = block_no;
DC[oldest].last_use = get_cache_time(this);
DC[oldest].dirty = 0;
/* Release the lock */
yield_lock_release(&this->lock);
/* And return success */
return E_SUCCESS;
}
/**
* ext2->write_block Write a block to the block device.
*
@ -401,71 +280,12 @@ static int write_block(ext2_fs_t * this, unsigned int block_no, uint8_t *buf) {
}
/* This operation requires the filesystem lock */
yield_lock_acquire(&this->lock);
if (!DC) {
write_fs(this->block_device, block_no * this->block_size, this->block_size, buf);
yield_lock_release(&this->lock);
return E_SUCCESS;
}
/* Find the entry in the cache */
int oldest = -1;
unsigned int oldest_age = UINT32_MAX;
for (unsigned int i = 0; i < this->cache_entries; ++i) {
if (DC[i].block_no == block_no) {
/* We found it. Update the cache entry */
DC[i].last_use = get_cache_time(this);
DC[i].dirty = 1;
memcpy(DC[i].block, buf, this->block_size);
yield_lock_release(&this->lock);
return E_SUCCESS;
}
if (DC[i].last_use < oldest_age) {
/* Keep track of the oldest entry */
oldest = i;
oldest_age = DC[i].last_use;
}
}
/* We did not find this element in the cache, so make room. */
if (DC[oldest].dirty) {
/* Flush the oldest entry */
cache_flush_dirty(this, oldest);
}
/* Update the entry */
memcpy(DC[oldest].block, buf, this->block_size);
DC[oldest].block_no = block_no;
DC[oldest].last_use = get_cache_time(this);
DC[oldest].dirty = 1;
/* Release the lock */
yield_lock_release(&this->lock);
/* We're done. */
return E_SUCCESS;
}
static unsigned int ext2_sync(ext2_fs_t * this) {
if (!this->disk_cache) return 0;
/* This operation requires the filesystem lock */
yield_lock_acquire(&this->lock);
/* Flush each cache entry. */
for (unsigned int i = 0; i < this->cache_entries; ++i) {
if (DC[i].dirty) {
cache_flush_dirty(this, i);
}
}
/* Release the lock */
yield_lock_release(&this->lock);
return 0;
}
/**
* ext2->set_block_number Set the "real" block number for a given "inode" block number.
*
@ -1052,8 +872,6 @@ static int mkdir_ext2(fs_node_t * parent, char * name, mode_t permission) {
write_block(this, this->bgd_offset + i, (uint8_t *)((uintptr_t)BGD + this->block_size * i));
}
ext2_sync(this);
return 0;
}
@ -1114,8 +932,6 @@ static int create_ext2(fs_node_t * parent, char * name, mode_t permission) {
free(inode);
ext2_sync(this);
return 0;
}
@ -1129,8 +945,6 @@ static int chmod_ext2(fs_node_t * node, mode_t mode) {
write_inode(this, inode, node->inode);
ext2_sync(this);
return 0;
}
@ -1291,8 +1105,6 @@ static int unlink_ext2(fs_node_t * node, char * name) {
inode_write_block(this, inode, node->inode, block_nr, block);
free(block);
ext2_sync(this);
return 0;
}
@ -1537,8 +1349,6 @@ static int symlink_ext2(fs_node_t * parent, char * target, char * name) {
}
free(inode);
ext2_sync(this);
return 0;
}
@ -1566,7 +1376,7 @@ static int ioctl_ext2(fs_node_t * node, unsigned long request, void * argp) {
switch (request) {
case IOCTLSYNC:
return ext2_sync(this);
return ioctl_fs(this->block_device, IOCTLSYNC, NULL);
default:
return -EINVAL;
@ -1739,11 +1549,6 @@ static fs_node_t * mount_ext2(fs_node_t * block_device, int flags) {
this->inode_size = 128;
}
this->block_size = 1024 << SB->log_block_size;
this->cache_entries = 10240;
if (this->block_size > 2048) {
this->cache_entries /= 4;
}
debug_print(INFO, "bs=%d, cache entries=%d", this->block_size, this->cache_entries);
this->pointers_per_block = this->block_size / 4;
debug_print(INFO, "Log block size = %d -> %d", SB->log_block_size, this->block_size);
BGDS = SB->blocks_count / SB->blocks_per_group;
@ -1752,26 +1557,6 @@ static fs_node_t * mount_ext2(fs_node_t * block_device, int flags) {
}
this->inodes_per_group = SB->inodes_count / BGDS;
if (!(this->flags & EXT2_FLAG_NOCACHE)) {
debug_print(INFO, "Allocating cache...");
DC = malloc(sizeof(ext2_disk_cache_entry_t) * this->cache_entries);
this->cache_data = malloc(this->block_size * this->cache_entries);
memset(this->cache_data, 0, this->block_size * this->cache_entries);
for (uint32_t i = 0; i < this->cache_entries; ++i) {
DC[i].block_no = 0;
DC[i].dirty = 0;
DC[i].last_use = 0;
DC[i].block = this->cache_data + i * this->block_size;
if (i % 128 == 0) {
debug_print(INFO, "Allocated cache block #%d", i+1);
}
}
debug_print(INFO, "Allocated cache.");
} else {
DC = NULL;
debug_print(NOTICE, "ext2 cache is disabled (nocache)");
}
// load the block group descriptors
this->bgd_block_span = sizeof(ext2_bgdescriptor_t) * BGDS / this->block_size + 1;
BGD = malloc(this->block_size * this->bgd_block_span);
@ -1839,9 +1624,6 @@ fs_node_t * ext2_fs_mount(const char * device, const char * mount_path) {
int flags = 0;
for (int i = 1; i < argc; ++i) {
if (!strcmp(argv[i],"nocache")) {
flags |= EXT2_FLAG_NOCACHE;
}
if (!strcmp(argv[i],"rw")) {
flags |= EXT2_FLAG_READWRITE;
}