[PATCH 1/7] nilfs2: drop null test before destroy functions

[Ryusuke Konishi]

From: Julia Lawall 

Remove unneeded NULL test.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// 
@@ expression x; @@
-if (x != NULL)
  \(kmem_cache_destroy\|mempool_destroy\|dma_pool_destroy\)(x);
// 

Signed-off-by: Julia Lawall 
Signed-off-by: Ryusuke Konishi 
---
 fs/nilfs2/super.c | 12 
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index f47585b..c69455a 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1405,14 +1405,10 @@ static void nilfs_destroy_cachep(void)
 */
rcu_barrier();
 
-   if (nilfs_inode_cachep)
-   kmem_cache_destroy(nilfs_inode_cachep);
-   if (nilfs_transaction_cachep)
-   kmem_cache_destroy(nilfs_transaction_cachep);
-   if (nilfs_segbuf_cachep)
-   kmem_cache_destroy(nilfs_segbuf_cachep);
-   if (nilfs_btree_path_cache)
-   kmem_cache_destroy(nilfs_btree_path_cache);
+   kmem_cache_destroy(nilfs_inode_cachep);
+   kmem_cache_destroy(nilfs_transaction_cachep);
+   kmem_cache_destroy(nilfs_segbuf_cachep);
+   kmem_cache_destroy(nilfs_btree_path_cache);
 }
 
 static int __init nilfs_init_cachep(void)
-- 
1.8.3.1

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[PATCH 6/7] nilfs2: add helper functions to delete blocks from dat file

[Ryusuke Konishi]

This adds delete functions for data blocks of metadata files using
bitmap based allocator.  nilfs_palloc_delete_entry_block() deletes an
entry block (e.g. block storing dat entries), and
nilfs_palloc_delete_bitmap_block() deletes a bitmap block,
respectively.

These helpers are intended to be used in the successive change on
deallocator of block addresses ("nilfs2: free unused dat file blocks
during garbage collection").

Signed-off-by: Ryusuke Konishi 
---
 fs/nilfs2/alloc.c | 50 ++
 1 file changed, 50 insertions(+)

diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index 5b7ee36..225b797 100644
--- a/fs/nilfs2/alloc.c
+++ b/fs/nilfs2/alloc.c
@@ -236,6 +236,26 @@ static int nilfs_palloc_get_block(struct inode *inode, 
unsigned long blkoff,
 }
 
 /**
+ * nilfs_palloc_delete_block - delete a block on the persistent allocator file
+ * @inode: inode of metadata file using this allocator
+ * @blkoff: block offset
+ * @prev: nilfs_bh_assoc struct of the last used buffer
+ * @lock: spin lock protecting @prev
+ */
+static int nilfs_palloc_delete_block(struct inode *inode, unsigned long blkoff,
+struct nilfs_bh_assoc *prev,
+spinlock_t *lock)
+{
+   spin_lock(lock);
+   if (prev->bh && blkoff == prev->blkoff) {
+   brelse(prev->bh);
+   prev->bh = NULL;
+   }
+   spin_unlock(lock);
+   return nilfs_mdt_delete_block(inode, blkoff);
+}
+
+/**
  * nilfs_palloc_get_desc_block - get buffer head of a group descriptor block
  * @inode: inode of metadata file using this allocator
  * @group: group number
@@ -274,6 +294,22 @@ static int nilfs_palloc_get_bitmap_block(struct inode 
*inode,
 }
 
 /**
+ * nilfs_palloc_delete_bitmap_block - delete a bitmap block
+ * @inode: inode of metadata file using this allocator
+ * @group: group number
+ */
+static int nilfs_palloc_delete_bitmap_block(struct inode *inode,
+   unsigned long group)
+{
+   struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+   return nilfs_palloc_delete_block(inode,
+nilfs_palloc_bitmap_blkoff(inode,
+   group),
+>prev_bitmap, >lock);
+}
+
+/**
  * nilfs_palloc_get_entry_block - get buffer head of an entry block
  * @inode: inode of metadata file using this allocator
  * @nr: serial number of the entry (e.g. inode number)
@@ -292,6 +328,20 @@ int nilfs_palloc_get_entry_block(struct inode *inode, 
__u64 nr,
 }
 
 /**
+ * nilfs_palloc_delete_entry_block - delete an entry block
+ * @inode: inode of metadata file using this allocator
+ * @nr: serial number of the entry
+ */
+static int nilfs_palloc_delete_entry_block(struct inode *inode, __u64 nr)
+{
+   struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+   return nilfs_palloc_delete_block(inode,
+nilfs_palloc_entry_blkoff(inode, nr),
+>prev_entry, >lock);
+}
+
+/**
  * nilfs_palloc_block_get_group_desc - get kernel address of a group descriptor
  * @inode: inode of metadata file using this allocator
  * @group: group number
-- 
1.8.3.1

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[PATCH 7/7] nilfs2: free unused dat file blocks during garbage collection

[Ryusuke Konishi]

As a nilfs2 volume ages, the amount of available disk space
decreases little by little due to bloat of DAT (disk address
translation) metadata file.  Even if we delete all files in a file
system and free their block addresses from the DAT file through a
garbage collection, empty DAT blocks are not freed.

This fixes the issue by extending the deallocator of block addresses
so that empty data blocks and empty bitmap blocks of DAT are deleted.

The following comparison shows the effect of this patch.  Each shows
disk amount information of a nilfs2 volume that we cleaned out by
deleting all files and running gc after having filled 90% of its
capacity.

Before:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1  500105212  3022844 472072192   1% /test

After:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1  50010521216380 475078656   1% /test

Signed-off-by: Ryusuke Konishi 
---
 fs/nilfs2/alloc.c | 91 ---
 fs/nilfs2/alloc.h |  1 +
 2 files changed, 75 insertions(+), 17 deletions(-)

diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index 225b797..b335a32 100644
--- a/fs/nilfs2/alloc.c
+++ b/fs/nilfs2/alloc.c
@@ -154,13 +154,17 @@ nilfs_palloc_group_desc_nfrees(const struct 
nilfs_palloc_group_desc *desc,
  * @lock: spin lock protecting @desc
  * @n: delta to be added
  */
-static void
+static u32
 nilfs_palloc_group_desc_add_entries(struct nilfs_palloc_group_desc *desc,
spinlock_t *lock, u32 n)
 {
+   u32 nfree;
+
spin_lock(lock);
le32_add_cpu(>pg_nfrees, n);
+   nfree = le32_to_cpu(desc->pg_nfrees);
spin_unlock(lock);
+   return nfree;
 }
 
 /**
@@ -735,12 +739,18 @@ int nilfs_palloc_freev(struct inode *inode, __u64 
*entry_nrs, size_t nitems)
unsigned char *bitmap;
void *desc_kaddr, *bitmap_kaddr;
unsigned long group, group_offset;
-   __u64 group_min_nr;
+   __u64 group_min_nr, last_nrs[8];
const unsigned long epg = nilfs_palloc_entries_per_group(inode);
+   const unsigned epb = NILFS_MDT(inode)->mi_entries_per_block;
+   unsigned entry_start, end, pos;
spinlock_t *lock;
-   int i, j, n, ret;
+   int i, j, k, ret;
+   u32 nfree;
 
for (i = 0; i < nitems; i = j) {
+   int change_group = false;
+   int nempties = 0, n = 0;
+
group = nilfs_palloc_group(inode, entry_nrs[i], _offset);
ret = nilfs_palloc_get_desc_block(inode, group, 0, _bh);
if (ret < 0)
@@ -755,17 +765,13 @@ int nilfs_palloc_freev(struct inode *inode, __u64 
*entry_nrs, size_t nitems)
/* Get the first entry number of the group */
group_min_nr = (__u64)group * epg;
 
-   desc_kaddr = kmap(desc_bh->b_page);
-   desc = nilfs_palloc_block_get_group_desc(
-   inode, group, desc_bh, desc_kaddr);
bitmap_kaddr = kmap(bitmap_bh->b_page);
bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
lock = nilfs_mdt_bgl_lock(inode, group);
-   for (j = i, n = 0;
-j < nitems && entry_nrs[j] >= group_min_nr &&
-entry_nrs[j] < group_min_nr + epg;
-j++) {
-   group_offset = entry_nrs[j] - group_min_nr;
+
+   j = i;
+   entry_start = rounddown(group_offset, epb);
+   do {
if (!nilfs_clear_bit_atomic(lock, group_offset,
bitmap)) {
nilfs_warning(inode->i_sb, __func__,
@@ -775,18 +781,69 @@ int nilfs_palloc_freev(struct inode *inode, __u64 
*entry_nrs, size_t nitems)
} else {
n++;
}
-   }
-   nilfs_palloc_group_desc_add_entries(desc, lock, n);
+
+   j++;
+   if (j >= nitems || entry_nrs[j] < group_min_nr ||
+   entry_nrs[j] >= group_min_nr + epg) {
+   change_group = true;
+   } else {
+   group_offset = entry_nrs[j] - group_min_nr;
+   if (group_offset >= entry_start &&
+   group_offset < entry_start + epb) {
+   /* This entry is in the same block */
+   continue;
+   }
+   }
+
+   /* Test if the entry block is empty or not */
+   end = entry_start + epb;
+   pos = nilfs_find_next_bit(bitmap, end, entry_start);
+   if (pos >= end) {
+