Btrfs: Add zlib compression support

This is a large change for adding compression on reading and writing,
both for inline and regular extents.  It does some fairly large
surgery to the writeback paths.

Compression is off by default and enabled by mount -o compress.  Even
when the -o compress mount option is not used, it is possible to read
compressed extents off the disk.

If compression for a given set of pages fails to make them smaller, the
file is flagged to avoid future compression attempts later.

* While finding delalloc extents, the pages are locked before being sent down
to the delalloc handler.  This allows the delalloc handler to do complex things
such as cleaning the pages, marking them writeback and starting IO on their
behalf.

* Inline extents are inserted at delalloc time now.  This allows us to compress
the data before inserting the inline extent, and it allows us to insert
an inline extent that spans multiple pages.

* All of the in-memory extent representations (extent_map.c, ordered-data.c etc)
are changed to record both an in-memory size and an on disk size, as well
as a flag for compression.

From a disk format point of view, the extent pointers in the file are changed
to record the on disk size of a given extent and some encoding flags.
Space in the disk format is allocated for compression encoding, as well
as encryption and a generic 'other' field.  Neither the encryption or the
'other' field are currently used.

In order to limit the amount of data read for a single random read in the
file, the size of a compressed extent is limited to 128k.  This is a
software only limit, the disk format supports u64 sized compressed extents.

In order to limit the ram consumed while processing extents, the uncompressed
size of a compressed extent is limited to 256k.  This is a software only limit
and will be subject to tuning later.

Checksumming is still done on compressed extents, and it is done on the
uncompressed version of the data.  This way additional encodings can be
layered on without having to figure out which encoding to checksum.

Compression happens at delalloc time, which is basically singled threaded because
it is usually done by a single pdflush thread.  This makes it tricky to
spread the compression load across all the cpus on the box.  We'll have to
look at parallel pdflush walks of dirty inodes at a later time.

Decompression is hooked into readpages and it does spread across CPUs nicely.

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

1 files changed, 13 insertions, 5 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 0be044bb6194..dc95f636a11b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -83,6 +83,7 @@ struct async_submit_bio {
         extent_submit_bio_hook_t *submit_bio_hook;
         int rw;
         int mirror_num;
+        unsigned long bio_flags;
         struct btrfs_work work;
 };
 
@@ -115,6 +116,7 @@ struct extent_map *btree_get_extent(struct inode *inode, struct page *page,
         }
         em->start = 0;
         em->len = (u64)-1;
+        em->block_len = (u64)-1;
         em->block_start = 0;
         em->bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
 
@@ -469,12 +471,13 @@ static void run_one_async_submit(struct btrfs_work *work)
                 wake_up(&fs_info->async_submit_wait);
 
         async->submit_bio_hook(async->inode, async->rw, async->bio,
-                               async->mirror_num);
+                               async->mirror_num, async->bio_flags);
         kfree(async);
 }
 
 int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
                         int rw, struct bio *bio, int mirror_num,
+                        unsigned long bio_flags,
                         extent_submit_bio_hook_t *submit_bio_hook)
 {
         struct async_submit_bio *async;
@@ -491,6 +494,7 @@ int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
         async->submit_bio_hook = submit_bio_hook;
         async->work.func = run_one_async_submit;
         async->work.flags = 0;
+        async->bio_flags = bio_flags;
 
         while(atomic_read(&fs_info->async_submit_draining) &&
               atomic_read(&fs_info->nr_async_submits)) {
@@ -530,7 +534,7 @@ static int btree_csum_one_bio(struct bio *bio)
 }
 
 static int __btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
-                                 int mirror_num)
+                                 int mirror_num, unsigned long bio_flags)
 {
         struct btrfs_root *root = BTRFS_I(inode)->root;
         int ret;
@@ -556,17 +560,17 @@ static int __btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
 }
 
 static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
-                                 int mirror_num)
+                                 int mirror_num, unsigned long bio_flags)
 {
         /*
          * kthread helpers are used to submit writes so that checksumming
          * can happen in parallel across all CPUs
          */
         if (!(rw & (1 << BIO_RW))) {
-                return __btree_submit_bio_hook(inode, rw, bio, mirror_num);
+                return __btree_submit_bio_hook(inode, rw, bio, mirror_num, 0);
         }
         return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
-                                   inode, rw, bio, mirror_num,
+                                   inode, rw, bio, mirror_num, 0,
                                    __btree_submit_bio_hook);
 }
 
@@ -1407,6 +1411,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         fs_info->btree_inode = new_inode(sb);
         fs_info->btree_inode->i_ino = 1;
         fs_info->btree_inode->i_nlink = 1;
+
         fs_info->thread_pool_size = min(num_online_cpus() + 2, 8);
 
         INIT_LIST_HEAD(&fs_info->ordered_extents);
@@ -1508,6 +1513,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
          */
         btrfs_init_workers(&fs_info->workers, "worker",
                            fs_info->thread_pool_size);
+
         btrfs_init_workers(&fs_info->submit_workers, "submit",
                            min_t(u64, fs_devices->num_devices,
                            fs_info->thread_pool_size));
@@ -1559,6 +1565,8 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         }
 
         fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
+        fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
+                                    4 * 1024 * 1024 / PAGE_CACHE_SIZE);
 
         nodesize = btrfs_super_nodesize(disk_super);
         leafsize = btrfs_super_leafsize(disk_super);