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-rw-r--r--fs/btrfs/compression.h30
1 files changed, 20 insertions, 10 deletions
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 09879579fbc8..39ec43ab8df1 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -19,20 +19,32 @@
#ifndef __BTRFS_COMPRESSION_
#define __BTRFS_COMPRESSION_
+/*
+ * We want to make sure that amount of RAM required to uncompress an extent is
+ * reasonable, so we limit the total size in ram of a compressed extent to
+ * 128k. This is a crucial number because it also controls how easily we can
+ * spread reads across cpus for decompression.
+ *
+ * We also want to make sure the amount of IO required to do a random read is
+ * reasonably small, so we limit the size of a compressed extent to 128k.
+ */
+
+/* Maximum length of compressed data stored on disk */
+#define BTRFS_MAX_COMPRESSED (SZ_128K)
+/* Maximum size of data before compression */
+#define BTRFS_MAX_UNCOMPRESSED (SZ_128K)
+
void btrfs_init_compress(void);
void btrfs_exit_compress(void);
int btrfs_compress_pages(int type, struct address_space *mapping,
- u64 start, unsigned long len,
- struct page **pages,
- unsigned long nr_dest_pages,
+ u64 start, struct page **pages,
unsigned long *out_pages,
unsigned long *total_in,
- unsigned long *total_out,
- unsigned long max_out);
+ unsigned long *total_out);
int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
unsigned long start_byte, size_t srclen, size_t destlen);
-int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
+int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
unsigned long total_out, u64 disk_start,
struct bio *bio);
@@ -59,13 +71,11 @@ struct btrfs_compress_op {
int (*compress_pages)(struct list_head *workspace,
struct address_space *mapping,
- u64 start, unsigned long len,
+ u64 start,
struct page **pages,
- unsigned long nr_dest_pages,
unsigned long *out_pages,
unsigned long *total_in,
- unsigned long *total_out,
- unsigned long max_out);
+ unsigned long *total_out);
int (*decompress_bio)(struct list_head *workspace,
struct page **pages_in,