ChangeLog, ext2_io.h, unix_io.c:
unix_io.c: Make massive changes to support a multiple block
writethrough cacheing.
ext2_io.h: Added flags field to the io_channel structure.
diff --git a/lib/ext2fs/ChangeLog b/lib/ext2fs/ChangeLog
index 33ce94c..39e4e9e 100644
--- a/lib/ext2fs/ChangeLog
+++ b/lib/ext2fs/ChangeLog
@@ -1,3 +1,10 @@
+2000-08-22 <tytso@valinux.com>
+
+ * unix_io.c: Make massive changes to support a multiple block
+ writethrough cacheing.
+
+ * ext2_io.h: Added flags field to the io_channel structure.
+
2000-08-19 <tytso@valinux.com>
* finddev.c, ext2fs.h, Makefile.in: Add new file, finddev.c, which
diff --git a/lib/ext2fs/ext2_io.h b/lib/ext2fs/ext2_io.h
index 9568866..49c09f3 100644
--- a/lib/ext2fs/ext2_io.h
+++ b/lib/ext2fs/ext2_io.h
@@ -27,6 +27,8 @@
typedef struct struct_io_manager *io_manager;
typedef struct struct_io_channel *io_channel;
+#define CHANNEL_FLAGS_WRITETHROUGH 0x01
+
struct struct_io_channel {
errcode_t magic;
io_manager manager;
@@ -47,7 +49,8 @@
int actual_bytes_written,
errcode_t error);
int refcount;
- int reserved[15];
+ int flags;
+ int reserved[14];
void *private_data;
void *app_data;
};
diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index e0cc4db..19c6926 100644
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -45,13 +45,24 @@
#define EXT2_CHECK_MAGIC(struct, code) \
if ((struct)->magic != (code)) return (code)
-
+
+struct unix_cache {
+ char *buf;
+ unsigned long block;
+ int access_time;
+ int dirty:1;
+ int in_use:1;
+};
+
+#define CACHE_SIZE 8
+#define WRITE_VIA_CACHE_SIZE 4 /* Must be smaller than CACHE_SIZE */
+
struct unix_private_data {
int magic;
int dev;
int flags;
- char *buf;
- int buf_block_nr;
+ int access_time;
+ struct unix_cache cache[CACHE_SIZE];
};
static errcode_t unix_open(const char *name, int flags, io_channel *channel);
@@ -76,6 +87,208 @@
io_manager unix_io_manager = &struct_unix_manager;
+/*
+ * Here are the raw I/O functions
+ */
+static errcode_t raw_read_blk(io_channel channel,
+ struct unix_private_data *data,
+ unsigned long block,
+ int count, void *buf)
+{
+ errcode_t retval;
+ size_t size;
+ ext2_loff_t location;
+ int actual = 0;
+
+ size = (count < 0) ? -count : count * channel->block_size;
+ location = (ext2_loff_t) block * channel->block_size;
+ if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+ retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
+ goto error_out;
+ }
+ actual = read(data->dev, buf, size);
+ if (actual != size) {
+ if (actual < 0)
+ actual = 0;
+ retval = EXT2_ET_SHORT_READ;
+ goto error_out;
+ }
+ return 0;
+
+error_out:
+ memset((char *) buf+actual, 0, size-actual);
+ if (channel->read_error)
+ retval = (channel->read_error)(channel, block, count, buf,
+ size, actual, retval);
+ return retval;
+}
+
+static errcode_t raw_write_blk(io_channel channel,
+ struct unix_private_data *data,
+ unsigned long block,
+ int count, const void *buf)
+{
+ size_t size;
+ ext2_loff_t location;
+ int actual = 0;
+ errcode_t retval;
+
+ if (count == 1)
+ size = channel->block_size;
+ else {
+ if (count < 0)
+ size = -count;
+ else
+ size = count * channel->block_size;
+ }
+
+ location = (ext2_loff_t) block * channel->block_size;
+ if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+ retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
+ goto error_out;
+ }
+
+ actual = write(data->dev, buf, size);
+ if (actual != size) {
+ retval = EXT2_ET_SHORT_WRITE;
+ goto error_out;
+ }
+ return 0;
+
+error_out:
+ if (channel->write_error)
+ retval = (channel->write_error)(channel, block, count, buf,
+ size, actual, retval);
+ return retval;
+}
+
+
+/*
+ * Here we implement the cache functions
+ */
+
+/* Allocate the cache buffers */
+static errcode_t alloc_cache(io_channel channel,
+ struct unix_private_data *data)
+{
+ errcode_t retval;
+ struct unix_cache *cache;
+ int i;
+
+ data->access_time = 0;
+ for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+ cache->block = 0;
+ cache->access_time = 0;
+ cache->dirty = 0;
+ cache->in_use = 0;
+ if ((retval = ext2fs_get_mem(channel->block_size,
+ (void **) &cache->buf)))
+ return retval;
+ }
+ return 0;
+}
+
+/* Free the cache buffers */
+static void free_cache(io_channel channel,
+ struct unix_private_data *data)
+{
+ struct unix_cache *cache;
+ int i;
+
+ data->access_time = 0;
+ for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+ cache->block = 0;
+ cache->access_time = 0;
+ cache->dirty = 0;
+ cache->in_use = 0;
+ if (cache->buf)
+ ext2fs_free_mem((void **) &cache->buf);
+ cache->buf = 0;
+ }
+}
+
+/*
+ * Try to find a block in the cache. If get_cache is non-zero, then
+ * if the block isn't in the cache, evict the oldest block in the
+ * cache and create a new cache entry for the requested block.
+ */
+struct unix_cache *find_cached_block(io_channel channel,
+ struct unix_private_data *data,
+ unsigned long block,
+ int get_cache)
+{
+ struct unix_cache *cache, *free_cache, *oldest_cache;
+ int i;
+
+ free_cache = oldest_cache = 0;
+ for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+ if (!cache->in_use) {
+ free_cache = cache;
+ continue;
+ }
+ if (cache->block == block) {
+ cache->access_time = ++data->access_time;
+ return cache;
+ }
+ if (!oldest_cache ||
+ (cache->access_time < oldest_cache->access_time))
+ oldest_cache = cache;
+ }
+ if (!get_cache)
+ return 0;
+
+ /*
+ * Try to allocate cache slot.
+ */
+ if (free_cache)
+ cache = free_cache;
+ else {
+ cache = oldest_cache;
+ if (cache->dirty)
+ raw_write_blk(channel, data,
+ cache->block, 1, cache->buf);
+ }
+ cache->in_use = 1;
+ cache->block = block;
+ cache->access_time = ++data->access_time;
+ return cache;
+}
+
+/*
+ * Flush all of the blocks in the cache
+ */
+static errcode_t flush_cached_blocks(io_channel channel,
+ struct unix_private_data *data,
+ int invalidate)
+
+{
+ struct unix_cache *cache;
+ errcode_t retval, retval2;
+ int i;
+
+ retval2 = 0;
+ for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+ if (!cache->in_use)
+ continue;
+
+ if (invalidate)
+ cache->in_use = 0;
+
+ if (!cache->dirty)
+ continue;
+
+ retval = raw_write_blk(channel, data,
+ cache->block, 1, cache->buf);
+ if (retval)
+ retval2 = retval;
+ else
+ cache->dirty = 0;
+ }
+ return retval2;
+}
+
+
+
static errcode_t unix_open(const char *name, int flags, io_channel *channel)
{
io_channel io = NULL;
@@ -110,11 +323,10 @@
memset(data, 0, sizeof(struct unix_private_data));
data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;
- retval = ext2fs_get_mem(io->block_size, (void **) &data->buf);
- data->buf_block_nr = -1;
- if (retval)
- goto cleanup;
+ if ((retval = alloc_cache(io, data)))
+ goto cleanup;
+
open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
#ifdef HAVE_OPEN64
data->dev = open64(name, open_flags);
@@ -129,13 +341,12 @@
return 0;
cleanup:
- if (io)
- ext2fs_free_mem((void **) &io);
if (data) {
- if (data->buf)
- ext2fs_free_mem((void **) &data->buf);
+ free_cache(io, data);
ext2fs_free_mem((void **) &data);
}
+ if (io)
+ ext2fs_free_mem((void **) &io);
return retval;
}
@@ -150,11 +361,12 @@
if (--channel->refcount > 0)
return 0;
-
+
+ retval = flush_cached_blocks(channel, data, 0);
+
if (close(data->dev) < 0)
retval = errno;
- if (data->buf)
- ext2fs_free_mem((void **) &data->buf);
+ free_cache(channel, data);
if (channel->private_data)
ext2fs_free_mem((void **) &channel->private_data);
if (channel->name)
@@ -173,12 +385,13 @@
EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
if (channel->block_size != blksize) {
- channel->block_size = blksize;
- ext2fs_free_mem((void **) &data->buf);
- retval = ext2fs_get_mem(blksize, (void **) &data->buf);
- if (retval)
+ if ((retval = flush_cached_blocks(channel, data, 0)))
return retval;
- data->buf_block_nr = -1;
+
+ channel->block_size = blksize;
+ free_cache(channel, data);
+ if ((retval = alloc_cache(channel, data)))
+ return retval;
}
return 0;
}
@@ -188,96 +401,111 @@
int count, void *buf)
{
struct unix_private_data *data;
+ struct unix_cache *cache;
errcode_t retval;
- size_t size;
- ext2_loff_t location;
- int actual = 0;
+ int i, j;
EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
data = (struct unix_private_data *) channel->private_data;
EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
/*
- * If it's in the cache, use it!
+ * If we're doing an odd-sized read, flush out the cache and
+ * then do a direct read.
*/
- if ((count == 1) && (block == data->buf_block_nr)) {
- memcpy(buf, data->buf, channel->block_size);
- return 0;
+ if (count < 0) {
+ if ((retval = flush_cached_blocks(channel, data, 0)))
+ return retval;
+ return raw_read_blk(channel, data, block, count, buf);
}
-#if 0
- printf("read_block %lu (%d)\n", block, count);
+
+ while (count > 0) {
+ /* If it's in the cache, use it! */
+ if ((cache = find_cached_block(channel, data, block, 0))) {
+#ifdef DEBUG
+ printf("Using cached block %d\n", block);
#endif
- size = (count < 0) ? -count : count * channel->block_size;
- location = (ext2_loff_t) block * channel->block_size;
- if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
- retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
- goto error_out;
- }
- actual = read(data->dev, buf, size);
- if (actual != size) {
- if (actual < 0)
- actual = 0;
- retval = EXT2_ET_SHORT_READ;
- goto error_out;
- }
- if (count == 1) {
- data->buf_block_nr = block;
- memcpy(data->buf, buf, size); /* Update the cache */
+ memcpy(buf, cache->buf, channel->block_size);
+ count--;
+ block++;
+ buf += channel->block_size;
+ continue;
+ }
+ /*
+ * Find the number of uncached blocks so we can do a
+ * single read request
+ */
+ for (i=1; i < count; i++)
+ if (find_cached_block(channel, data, block+i, 0))
+ break;
+#ifdef DEBUG
+ printf("Reading %d blocks starting at %d\n", i, block);
+#endif
+ if ((retval = raw_read_blk(channel, data, block, i, buf)))
+ return retval;
+
+ /* Save the results in the cache */
+ for (j=0; j < i; j++) {
+ count--;
+ cache = find_cached_block(channel, data, block++, 1);
+ if (cache)
+ memcpy(cache->buf, buf, channel->block_size);
+ buf += channel->block_size;
+ }
}
return 0;
-
-error_out:
- memset((char *) buf+actual, 0, size-actual);
- if (channel->read_error)
- retval = (channel->read_error)(channel, block, count, buf,
- size, actual, retval);
- return retval;
}
static errcode_t unix_write_blk(io_channel channel, unsigned long block,
int count, const void *buf)
{
struct unix_private_data *data;
- size_t size;
- ext2_loff_t location;
- int actual = 0;
- errcode_t retval;
+ struct unix_cache *cache;
+ errcode_t retval = 0, retval2;
+ char *cp;
+ int i, writethrough;
EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
data = (struct unix_private_data *) channel->private_data;
EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
- if (count == 1)
- size = channel->block_size;
- else {
- data->buf_block_nr = -1; /* Invalidate the cache */
- if (count < 0)
- size = -count;
- else
- size = count * channel->block_size;
- }
-
- location = (ext2_loff_t) block * channel->block_size;
- if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
- retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
- goto error_out;
- }
-
- actual = write(data->dev, buf, size);
- if (actual != size) {
- retval = EXT2_ET_SHORT_WRITE;
- goto error_out;
+ /*
+ * If we're doing an odd-sized write or a very large write,
+ * flush out the cache completely and then do a direct write.
+ */
+ if (count < 0 || count > WRITE_VIA_CACHE_SIZE) {
+ if ((retval = flush_cached_blocks(channel, data, 1)))
+ return retval;
+ return raw_write_blk(channel, data, block, count, buf);
}
- if ((count == 1) && (block == data->buf_block_nr))
- memcpy(data->buf, buf, size); /* Update the cache */
+ /*
+ * For a moderate-sized multi-block write, first force a write
+ * if we're in write-through cache mode, and then fill the
+ * cache with the blocks.
+ */
+ writethrough = channel->flags & CHANNEL_FLAGS_WRITETHROUGH;
+ if (writethrough)
+ retval = raw_write_blk(channel, data, block, count, buf);
- return 0;
-
-error_out:
- if (channel->write_error)
- retval = (channel->write_error)(channel, block, count, buf,
- size, actual, retval);
+ while (count > 0) {
+ cache = find_cached_block(channel, data, block, 1);
+ if (!cache) {
+ /*
+ * Oh shit, we couldn't get cache descriptor.
+ * Force the write directly.
+ */
+ if ((retval2 = raw_write_blk(channel, data, block,
+ 1, buf)))
+ retval = retval2;
+ } else {
+ memcpy(cache->buf, buf, channel->block_size);
+ cache->dirty = !writethrough;
+ }
+ count--;
+ block++;
+ buf += channel->block_size;
+ }
return retval;
}
@@ -287,12 +515,14 @@
static errcode_t unix_flush(io_channel channel)
{
struct unix_private_data *data;
+ errcode_t retval = 0;
EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
data = (struct unix_private_data *) channel->private_data;
EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
-
+
+ retval = flush_cached_blocks(channel, data, 0);
fsync(data->dev);
- return 0;
+ return retval;
}