[PATCH] Squashfs: add asynchronous read support
From: Chanho Min
Date: Mon Dec 16 2013 - 00:32:56 EST
This patch removes synchronous wait for the up-to-date of buffer in the
file system level. Instead all operations after submit_bh are moved into
the End-of-IO handler and its associated workeque. It decompresses/copies
data into pages and unlock them asynchronously.
This patch enhances the performance of Squashfs in most cases.
Especially, large file reading is improved significantly.
dd read test:
- ARM cortex-a9 1GHz, 2 cores, eMMC 4.5 HS200 mode.
- dd if=file1 of=/dev/null bs=64k
Before
58707718 bytes (56.0MB) copied, 1.393653 seconds, 40.2MB/s
After
58707718 bytes (56.0MB) copied, 0.942413 seconds, 59.4MB/s
Signed-off-by: Chanho Min <chanho.min@xxxxxxx>
---
fs/squashfs/Kconfig | 9 ++
fs/squashfs/block.c | 262 +++++++++++++++++++++++++++++++++++++++++++++
fs/squashfs/file_direct.c | 8 +-
fs/squashfs/page_actor.c | 3 +-
fs/squashfs/page_actor.h | 3 +-
fs/squashfs/squashfs.h | 2 +
6 files changed, 284 insertions(+), 3 deletions(-)
diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
index b6fa865..284aa5a 100644
--- a/fs/squashfs/Kconfig
+++ b/fs/squashfs/Kconfig
@@ -51,6 +51,15 @@ config SQUASHFS_FILE_DIRECT
it eliminates a memcpy and it also removes the lock contention
on the single buffer.
+config SQUASHFS_READ_DATA_ASYNC
+ bool "Read and decompress data asynchronously"
+ depends on SQUASHFS_FILE_DIRECT
+ help
+ By default Squashfs read data synchronously by block (default 128k).
+ This option removes such a synchronous wait in the file system level.
+ All works after submit IO do at the End-of-IO handler asynchronously.
+ This enhances the performance of Squashfs in most cases, especially,
+ large file reading.
endchoice
choice
diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index 0cea9b9..1517ca3 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -212,3 +212,265 @@ read_failure:
kfree(bh);
return -EIO;
}
+
+#ifdef CONFIG_SQUASHFS_READ_DATA_ASYNC
+
+struct squashfs_end_io_assoc {
+ int offset;
+ int b_count;
+ int compressed;
+ int length;
+ struct squashfs_page_actor *p_actor;
+ struct buffer_head **__bh;
+ struct squashfs_sb_info *msblk;
+ struct work_struct read_work;
+};
+
+static int squashfs_copy_page(struct squashfs_sb_info *msblk,
+ struct buffer_head **bh, int b, int offset, int length,
+ struct squashfs_page_actor *output)
+{
+ /*
+ * Block is uncompressed.
+ */
+ int in, pg_offset = 0, avail = 0, bytes, k = 0;
+ void *data = squashfs_first_page(output);
+ for (bytes = length; k < b; k++) {
+ in = min(bytes, msblk->devblksize - offset);
+ bytes -= in;
+ while (in) {
+ if (pg_offset == PAGE_CACHE_SIZE) {
+ data = squashfs_next_page(output);
+ pg_offset = 0;
+ }
+ avail = min_t(int, in, PAGE_CACHE_SIZE -
+ pg_offset);
+ memcpy(data + pg_offset, bh[k]->b_data + offset,
+ avail);
+ in -= avail;
+ pg_offset += avail;
+ offset += avail;
+ }
+ offset = 0;
+ put_bh(bh[k]);
+ }
+ squashfs_finish_page(output);
+ return length;
+}
+
+/*
+ * This is executed in workqueue for squashfs_read_data_async().
+ * - pages come decompressed/copied and unlocked asynchronously.
+ */
+static void squashfs_buffer_read_async(struct squashfs_end_io_assoc *io_assoc)
+{
+ struct squashfs_sb_info *msblk = io_assoc->msblk;
+ struct squashfs_page_actor *actor = io_assoc->p_actor;
+ struct page **page = actor->page;
+ int pages = actor->pages;
+ struct page *target_page = actor->target_page;
+ int i, length, bytes = 0;
+ void *pageaddr;
+
+ if (io_assoc->compressed) {
+ length = squashfs_decompress(msblk, io_assoc->__bh,
+ io_assoc->b_count, io_assoc->offset,
+ io_assoc->length, actor);
+ if (length < 0) {
+ ERROR("squashfs_read_data failed to read block\n");
+ goto read_failure;
+ }
+ } else
+ length = squashfs_copy_page(msblk, io_assoc->__bh,
+ io_assoc->b_count, io_assoc->offset,
+ io_assoc->length, actor);
+
+ /* Last page may have trailing bytes not filled */
+ bytes = length % PAGE_CACHE_SIZE;
+ if (bytes) {
+ pageaddr = kmap_atomic(page[pages - 1]);
+ memset(pageaddr + bytes, 0, PAGE_CACHE_SIZE - bytes);
+ kunmap_atomic(pageaddr);
+ }
+
+ /* Mark pages as uptodate, unlock and release */
+ for (i = 0; i < pages; i++) {
+ flush_dcache_page(page[i]);
+ SetPageUptodate(page[i]);
+ unlock_page(page[i]);
+ if (page[i] != target_page)
+ page_cache_release(page[i]);
+ }
+
+ kfree(io_assoc->__bh);
+ kfree(actor);
+ kfree(page);
+ kfree(io_assoc);
+ return;
+
+read_failure:
+ /* Decompression failed, mark pages as errored. Target_page is
+ * dealt with by the caller
+ */
+ for (i = 0; i < pages; i++) {
+ if (page[i] == NULL || page[i] == target_page)
+ continue;
+ flush_dcache_page(page[i]);
+ SetPageError(page[i]);
+ unlock_page(page[i]);
+ page_cache_release(page[i]);
+ }
+
+ kfree(io_assoc->__bh);
+ kfree(actor);
+ kfree(page);
+ kfree(io_assoc);
+ return;
+}
+
+static void squashfs_async_work(struct work_struct *work)
+{
+ struct squashfs_end_io_assoc *io_assoc =
+ container_of(work, struct squashfs_end_io_assoc, read_work);
+
+ squashfs_buffer_read_async(io_assoc);
+}
+
+/*
+ * squashfs_buffer_end_io: update buffer and check if all buffers of array
+ * are updated then invoke the wq for async read.
+ */
+static void squashfs_buffer_end_io(struct buffer_head *bh, int uptodate)
+{
+ int i;
+ struct squashfs_end_io_assoc *io_assoc = bh->b_private;
+
+ if (uptodate) {
+ set_buffer_uptodate(bh);
+ } else {
+ /* This happens, due to failed READA attempts. */
+ clear_buffer_uptodate(bh);
+ }
+ unlock_buffer(bh);
+ put_bh(bh);
+
+ BUG_ON(!io_assoc);
+
+ /* Check if all buffers are uptodate */
+ for (i = 0; i < io_assoc->b_count; i++)
+ if (!buffer_uptodate(io_assoc->__bh[i]))
+ return;
+
+ schedule_work(&io_assoc->read_work);
+}
+
+/*
+ * squashfs_ll_r_block: low-level access to block devices for squashfs.
+ * @nr: number of &struct buffer_heads in the array
+ * @bhs: array of pointers to &struct buffer_head
+ *
+ * squashfs_ll_r_block sets b_end_io to the squashfs specific completion handler
+ * that marks the buffer up-to-date and invokes workqueue for decompression
+ * and uptodate of pages if needed.
+ */
+static void squashfs_ll_r_block(int nr, struct buffer_head *bhs[])
+{
+ int i, s_nr = 0;
+ struct squashfs_end_io_assoc *io_assoc = NULL;
+
+ for (i = 0; i < nr; i++) {
+ struct buffer_head *bh = bhs[i];
+ io_assoc = bh->b_private;
+ if (!trylock_buffer(bh))
+ continue;
+ if (!buffer_uptodate(bh)) {
+ bh->b_end_io = squashfs_buffer_end_io;
+ get_bh(bh);
+ s_nr++;
+ submit_bh(READ, bh);
+ continue;
+ }
+ unlock_buffer(bh);
+ }
+ /*
+ * All buffers are uptodate, but no submit_bh is occurred.
+ * Then try to unlock pages directly.
+ */
+ if (nr && !s_nr && io_assoc)
+ squashfs_buffer_read_async(io_assoc);
+}
+
+/*
+ * Read and datablock asynchronously. same as squashfs_read_data(),
+ * except it doesn't block until a buffer comes unlocked.
+ * the work after submit IO do at the End-Of-Handle and the associated wq.
+ */
+int squashfs_read_data_async(struct super_block *sb, u64 index, int length,
+ struct squashfs_page_actor *output)
+{
+ struct squashfs_sb_info *msblk = sb->s_fs_info;
+ struct buffer_head **bh;
+ int offset = index & ((1 << msblk->devblksize_log2) - 1);
+ u64 cur_index = index >> msblk->devblksize_log2;
+ int bytes, compressed, b = 0, k = 0;
+ struct squashfs_end_io_assoc *io_assoc;
+
+ bh = kcalloc(((output->length + msblk->devblksize - 1)
+ >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
+ if (bh == NULL)
+ return -ENOMEM;
+
+ if (!length)
+ return -EINVAL;
+
+ bytes = -offset;
+
+ compressed = SQUASHFS_COMPRESSED_BLOCK(length);
+ length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
+
+ TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
+ index, compressed ? "" : "un", length, output->length);
+
+ if (length < 0 || length > output->length ||
+ (index + length) > msblk->bytes_used)
+ goto read_failure;
+
+ io_assoc = kmalloc(sizeof(struct squashfs_end_io_assoc), GFP_KERNEL);
+ if (io_assoc == NULL)
+ return -ENOMEM;
+
+ io_assoc->offset = offset;
+ io_assoc->p_actor = output;
+ io_assoc->compressed = compressed;
+ io_assoc->__bh = bh;
+ io_assoc->length = length;
+ io_assoc->msblk = msblk;
+
+ INIT_WORK(&io_assoc->read_work, squashfs_async_work);
+
+ for (b = 0; bytes < length; b++, cur_index++) {
+ bh[b] = sb_getblk(sb, cur_index);
+ if (bh[b] == NULL)
+ goto block_release;
+ bytes += msblk->devblksize;
+ if (!buffer_locked(bh[b]))
+ bh[b]->b_private = io_assoc;
+ }
+ io_assoc->b_count = b;
+
+ /* make sure io_assoc is updated before submit IO */
+ mb();
+ squashfs_ll_r_block(b, bh);
+ return length;
+
+block_release:
+ for (; k < b; k++)
+ put_bh(bh[k]);
+
+read_failure:
+ ERROR("squashfs_read_data failed to read block 0x%llx\n",
+ (unsigned long long) index);
+ kfree(bh);
+ return -EIO;
+}
+#endif
diff --git a/fs/squashfs/file_direct.c b/fs/squashfs/file_direct.c
index 62a0de6..610ca17 100644
--- a/fs/squashfs/file_direct.c
+++ b/fs/squashfs/file_direct.c
@@ -52,7 +52,7 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize)
* Create a "page actor" which will kmap and kunmap the
* page cache pages appropriately within the decompressor
*/
- actor = squashfs_page_actor_init_special(page, pages, 0);
+ actor = squashfs_page_actor_init_special(page, pages, target_page, 0);
if (actor == NULL)
goto out;
@@ -91,6 +91,11 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize)
}
/* Decompress directly into the page cache buffers */
+#ifdef CONFIG_SQUASHFS_READ_DATA_ASYNC
+ squashfs_read_data_async(inode->i_sb, block, bsize, actor);
+
+ return 0;
+#else
res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
if (res < 0)
goto mark_errored;
@@ -116,6 +121,7 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize)
kfree(page);
return 0;
+#endif
mark_errored:
/* Decompression failed, mark pages as errored. Target_page is
diff --git a/fs/squashfs/page_actor.c b/fs/squashfs/page_actor.c
index 5a1c11f..2d2d7ac 100644
--- a/fs/squashfs/page_actor.c
+++ b/fs/squashfs/page_actor.c
@@ -81,7 +81,7 @@ static void direct_finish_page(struct squashfs_page_actor *actor)
}
struct squashfs_page_actor *squashfs_page_actor_init_special(struct page **page,
- int pages, int length)
+ int pages, struct page *target_page, int length)
{
struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
@@ -91,6 +91,7 @@ struct squashfs_page_actor *squashfs_page_actor_init_special(struct page **page,
actor->length = length ? : pages * PAGE_CACHE_SIZE;
actor->page = page;
actor->pages = pages;
+ actor->target_page = target_page;
actor->next_page = 0;
actor->pageaddr = NULL;
actor->squashfs_first_page = direct_first_page;
diff --git a/fs/squashfs/page_actor.h b/fs/squashfs/page_actor.h
index 26dd820..b50d982 100644
--- a/fs/squashfs/page_actor.h
+++ b/fs/squashfs/page_actor.h
@@ -58,13 +58,14 @@ struct squashfs_page_actor {
void *(*squashfs_next_page)(struct squashfs_page_actor *);
void (*squashfs_finish_page)(struct squashfs_page_actor *);
int pages;
+ struct page *target_page;
int length;
int next_page;
};
extern struct squashfs_page_actor *squashfs_page_actor_init(void **, int, int);
extern struct squashfs_page_actor *squashfs_page_actor_init_special(struct page
- **, int, int);
+ **, int, struct page *, int);
static inline void *squashfs_first_page(struct squashfs_page_actor *actor)
{
return actor->squashfs_first_page(actor);
diff --git a/fs/squashfs/squashfs.h b/fs/squashfs/squashfs.h
index 9e1bb79..39e95af 100644
--- a/fs/squashfs/squashfs.h
+++ b/fs/squashfs/squashfs.h
@@ -30,6 +30,8 @@
/* block.c */
extern int squashfs_read_data(struct super_block *, u64, int, u64 *,
struct squashfs_page_actor *);
+extern int squashfs_read_data_async(struct super_block *, u64, int,
+ struct squashfs_page_actor *);
/* cache.c */
extern struct squashfs_cache *squashfs_cache_init(char *, int, int);
--
1.7.9.5
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