linux-ext4 - [PATCH v2 8/8] ext4: Remove the logic to trim inode PAs

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Date:   Sat, 15 Oct 2022 02:06:30 +0530
From:   Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To:     linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>
Cc:     Ritesh Harjani <riteshh@...ux.ibm.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, rookxu <brookxu.cn@...il.com>,
        Ritesh Harjani <ritesh.list@...il.com>
Subject: [PATCH v2 8/8] ext4: Remove the logic to trim inode PAs

Earlier, inode PAs were stored in a linked list. This caused a need to
periodically trim the list down inorder to avoid growing it to a very
large size, as this would severly affect performance during list
iteration.

Recent patches changed this list to an rbtree, and since the tree scales
up much better, we no longer need to have the trim functionality, hence
remove it.

Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
Reviewed-by: Jan Kara <jack@...e.cz>
---
 Documentation/admin-guide/ext4.rst |  3 ---
 fs/ext4/ext4.h                     |  1 -
 fs/ext4/mballoc.c                  | 20 --------------------
 fs/ext4/mballoc.h                  |  5 -----
 fs/ext4/sysfs.c                    |  2 --
 5 files changed, 31 deletions(-)

diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst
index 4c559e08d11e..5740d85439ff 100644
--- a/Documentation/admin-guide/ext4.rst
+++ b/Documentation/admin-guide/ext4.rst
@@ -489,9 +489,6 @@ Files in /sys/fs/ext4/<devname>:
         multiple of this tuning parameter if the stripe size is not set in the
         ext4 superblock
 
-  mb_max_inode_prealloc
-        The maximum length of per-inode ext4_prealloc_space list.
-
   mb_max_to_scan
         The maximum number of extents the multiblock allocator will search to
         find the best extent.
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index c23be3b45442..1d2ed29278e2 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1612,7 +1612,6 @@ struct ext4_sb_info {
 	unsigned int s_mb_stats;
 	unsigned int s_mb_order2_reqs;
 	unsigned int s_mb_group_prealloc;
-	unsigned int s_mb_max_inode_prealloc;
 	unsigned int s_max_dir_size_kb;
 	/* where last allocation was done - for stream allocation */
 	unsigned long s_mb_last_group;
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 9bbe2e099d81..f2c004659258 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3419,7 +3419,6 @@ int ext4_mb_init(struct super_block *sb)
 	sbi->s_mb_stats = MB_DEFAULT_STATS;
 	sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD;
 	sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS;
-	sbi->s_mb_max_inode_prealloc = MB_DEFAULT_MAX_INODE_PREALLOC;
 	/*
 	 * The default group preallocation is 512, which for 4k block
 	 * sizes translates to 2 megabytes.  However for bigalloc file
@@ -5526,29 +5525,11 @@ static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac)
 	return ;
 }
 
-/*
- * if per-inode prealloc list is too long, trim some PA
- */
-static void ext4_mb_trim_inode_pa(struct inode *inode)
-{
-	struct ext4_inode_info *ei = EXT4_I(inode);
-	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-	int count, delta;
-
-	count = atomic_read(&ei->i_prealloc_active);
-	delta = (sbi->s_mb_max_inode_prealloc >> 2) + 1;
-	if (count > sbi->s_mb_max_inode_prealloc + delta) {
-		count -= sbi->s_mb_max_inode_prealloc;
-		ext4_discard_preallocations(inode, count);
-	}
-}
-
 /*
  * release all resource we used in allocation
  */
 static int ext4_mb_release_context(struct ext4_allocation_context *ac)
 {
-	struct inode *inode = ac->ac_inode;
 	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
 	struct ext4_prealloc_space *pa = ac->ac_pa;
 	if (pa) {
@@ -5584,7 +5565,6 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
 	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
 		mutex_unlock(&ac->ac_lg->lg_mutex);
 	ext4_mb_collect_stats(ac);
-	ext4_mb_trim_inode_pa(inode);
 	return 0;
 }
 
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index f8e8ee493867..6d85ee8674a6 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -73,11 +73,6 @@
  */
 #define MB_DEFAULT_GROUP_PREALLOC	512
 
-/*
- * maximum length of inode prealloc list
- */
-#define MB_DEFAULT_MAX_INODE_PREALLOC	512
-
 /*
  * Number of groups to search linearly before performing group scanning
  * optimization.
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index d233c24ea342..f0d42cf44c71 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -214,7 +214,6 @@ EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan);
 EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs);
 EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request);
 EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc);
-EXT4_RW_ATTR_SBI_UI(mb_max_inode_prealloc, s_mb_max_inode_prealloc);
 EXT4_RW_ATTR_SBI_UI(mb_max_linear_groups, s_mb_max_linear_groups);
 EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb);
 EXT4_ATTR(trigger_fs_error, 0200, trigger_test_error);
@@ -264,7 +263,6 @@ static struct attribute *ext4_attrs[] = {
 	ATTR_LIST(mb_order2_req),
 	ATTR_LIST(mb_stream_req),
 	ATTR_LIST(mb_group_prealloc),
-	ATTR_LIST(mb_max_inode_prealloc),
 	ATTR_LIST(mb_max_linear_groups),
 	ATTR_LIST(max_writeback_mb_bump),
 	ATTR_LIST(extent_max_zeroout_kb),
-- 
2.31.1