Merge git://git.kernel.org/pub/scm/linux/kernel/git/pkl/squashfs-next

* git://git.kernel.org/pub/scm/linux/kernel/git/pkl/squashfs-next:
  Squashfs: Add an option to set dev block size to 4K

3 files changed, 30 insertions, 1 deletions

diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
index 048b59d5b2f..c70111ebefd 100644
--- a/fs/squashfs/Kconfig
+++ b/fs/squashfs/Kconfig
@@ -78,6 +78,28 @@ config SQUASHFS_XZ
 
           If unsure, say N.
 
+config SQUASHFS_4K_DEVBLK_SIZE
+        bool "Use 4K device block size?"
+        depends on SQUASHFS
+        help
+          By default Squashfs sets the dev block size (sb_min_blocksize)
+          to 1K or the smallest block size supported by the block device
+          (if larger).  This, because blocks are packed together and
+          unaligned in Squashfs, should reduce latency.
+
+          This, however, gives poor performance on MTD NAND devices where
+          the optimal I/O size is 4K (even though the devices can support
+          smaller block sizes).
+
+          Using a 4K device block size may also improve overall I/O
+          performance for some file access patterns (e.g. sequential
+          accesses of files in filesystem order) on all media.
+
+          Setting this option will force Squashfs to use a 4K device block
+          size by default.
+
+          If unsure, say N.
+
 config SQUASHFS_EMBEDDED
         bool "Additional option for memory-constrained systems"
         depends on SQUASHFS
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index b4a4e539a08..e8e14645de9 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -36,6 +36,13 @@
 #define SQUASHFS_FILE_SIZE              131072
 #define SQUASHFS_FILE_LOG               17
 
+/* default size of block device I/O */
+#ifdef CONFIG_SQUASHFS_4K_DEVBLK_SIZE
+#define SQUASHFS_DEVBLK_SIZE 4096
+#else
+#define SQUASHFS_DEVBLK_SIZE 1024
+#endif
+
 #define SQUASHFS_FILE_MAX_SIZE          1048576
 #define SQUASHFS_FILE_MAX_LOG           20
 
diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 7438850c62d..2da1715452a 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -95,7 +95,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
         }
         msblk = sb->s_fs_info;
 
-        msblk->devblksize = sb_min_blocksize(sb, BLOCK_SIZE);
+        msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
         msblk->devblksize_log2 = ffz(~msblk->devblksize);
 
         mutex_init(&msblk->read_data_mutex);