Btrfs: Add mount -o compress-force

The default btrfs mount -o compress mode will quickly back off
compressing a file if it notices that compression does not reduce the
size of the data being written.  This can save considerable CPU because
all future writes to the file go through uncompressed.

But some files are both very large and have mixed data stored in
them.  In that case, we want to add the ability to always try
compressing data before writing it.

This commit adds mount -o compress-force.  A later commit will add
a new inode flag that does the same thing.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 9f806dd04c2704899bf28e5324eebaa14a923e27..2aa8ec6a09812051ba5578092c608c3d0c460535 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1161,6 +1161,7 @@ struct btrfs_root {
 #define BTRFS_MOUNT_SSD_SPREAD         (1 << 8)
 #define BTRFS_MOUNT_NOSSD              (1 << 9)
 #define BTRFS_MOUNT_DISCARD            (1 << 10)
+#define BTRFS_MOUNT_FORCE_COMPRESS      (1 << 11)
 
 #define btrfs_clear_opt(o, opt)                ((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)          ((o) |= BTRFS_MOUNT_##opt)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b330e27c2d8b01e3e3b619266936ebd927918297..f46c572768445d056783ac7db47a851b86d322dd 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -483,7 +483,8 @@ again:
                nr_pages_ret = 0;
 
                /* flag the file so we don't compress in the future */
-               BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS;
+               if (!btrfs_test_opt(root, FORCE_COMPRESS))
+                       BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS;
        }
        if (will_compress) {
                *num_added += 1;

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 3f9b45704fcdfb83eeda6a55740c56de7a048ce5..8a1ea6e64575a34c507c29cd8c84ec4944885583 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -66,7 +66,8 @@ enum {
        Opt_degraded, Opt_subvol, Opt_device, Opt_nodatasum, Opt_nodatacow,
        Opt_max_extent, Opt_max_inline, Opt_alloc_start, Opt_nobarrier,
        Opt_ssd, Opt_nossd, Opt_ssd_spread, Opt_thread_pool, Opt_noacl,
-       Opt_compress, Opt_notreelog, Opt_ratio, Opt_flushoncommit,
+       Opt_compress, Opt_compress_force, Opt_notreelog, Opt_ratio,
+       Opt_flushoncommit,
        Opt_discard, Opt_err,
 };
 
@@ -82,6 +83,7 @@ static match_table_t tokens = {
        {Opt_alloc_start, "alloc_start=%s"},
        {Opt_thread_pool, "thread_pool=%d"},
        {Opt_compress, "compress"},
+       {Opt_compress_force, "compress-force"},
        {Opt_ssd, "ssd"},
        {Opt_ssd_spread, "ssd_spread"},
        {Opt_nossd, "nossd"},
@@ -173,6 +175,11 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                        printk(KERN_INFO "btrfs: use compression\n");
                        btrfs_set_opt(info->mount_opt, COMPRESS);
                        break;
+               case Opt_compress_force:
+                       printk(KERN_INFO "btrfs: forcing compression\n");
+                       btrfs_set_opt(info->mount_opt, FORCE_COMPRESS);
+                       btrfs_set_opt(info->mount_opt, COMPRESS);
+                       break;
                case Opt_ssd:
                        printk(KERN_INFO "btrfs: use ssd allocation scheme\n");
                        btrfs_set_opt(info->mount_opt, SSD);