[PATCH 5.16 143/164] btrfs: autodefrag: only scan one inode once

Greg Kroah-Hartman
2022-02-28T18:13:08Z

From: Qu Wenruo <wqu@suse.com>

commit 26fbac2517fcad34fa3f950151fd4c0240fb2935 upstream.

Although we have btrfs_requeue_inode_defrag(), for autodefrag we are
still just exhausting all inode_defrag items in the tree.

This means, it doesn't make much difference to requeue an inode_defrag,
other than scan the inode from the beginning till its end.

Change the behaviour to always scan from offset 0 of an inode, and till
the end.

By this we get the following benefit:

- Straight-forward code

- No more re-queue related check

- Fewer members in inode_defrag

We still keep the same btrfs_get_fs_root() and btrfs_iget() check for
each loop, and added extra should_auto_defrag() check per-loop.

Note: the patch needs to be backported and is intentionally written
to minimize the diff size, code will be cleaned up later.

CC: stable@vger.kernel.org # 5.16
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/file.c | 84 ++++++++++++++------------------------------------------
1 file changed, 22 insertions(+), 62 deletions(-)

--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -49,12 +49,6 @@ struct inode_defrag {

/* root objectid */
u64 root;
-
- /* last offset we were able to defrag */
- u64 last_offset;
-
- /* if we've wrapped around back to zero once already */
- int cycled;
};

static int __compare_inode_defrag(struct inode_defrag *defrag1,
@@ -107,8 +101,6 @@ static int __btrfs_add_inode_defrag(stru
*/
if (defrag->transid < entry->transid)
entry->transid = defrag->transid;
- if (defrag->last_offset > entry->last_offset)
- entry->last_offset = defrag->last_offset;
return -EEXIST;
}
}
@@ -179,34 +171,6 @@ int btrfs_add_inode_defrag(struct btrfs_
}

/*
- * Requeue the defrag object. If there is a defrag object that points to
- * the same inode in the tree, we will merge them together (by
- * __btrfs_add_inode_defrag()) and free the one that we want to requeue.
- */
-static void btrfs_requeue_inode_defrag(struct btrfs_inode *inode,
- struct inode_defrag *defrag)
-{
- struct btrfs_fs_info *fs_info = inode->root->fs_info;
- int ret;
-
- if (!__need_auto_defrag(fs_info))
- goto out;
-
- /*
- * Here we don't check the IN_DEFRAG flag, because we need merge
- * them together.
- */
- spin_lock(&fs_info->defrag_inodes_lock);
- ret = __btrfs_add_inode_defrag(inode, defrag);
- spin_unlock(&fs_info->defrag_inodes_lock);
- if (ret)
- goto out;
- return;
-out:
- kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
-}
-
-/*
* pick the defragable inode that we want, if it doesn't exist, we will get
* the next one.
*/
@@ -278,8 +242,14 @@ static int __btrfs_run_defrag_inode(stru
struct btrfs_root *inode_root;
struct inode *inode;
struct btrfs_ioctl_defrag_range_args range;
- int num_defrag;
- int ret;
+ int ret = 0;
+ u64 cur = 0;
+
+again:
+ if (test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state))
+ goto cleanup;
+ if (!__need_auto_defrag(fs_info))
+ goto cleanup;

/* get the inode */
inode_root = btrfs_get_fs_root(fs_info, defrag->root, true);
@@ -295,39 +265,29 @@ static int __btrfs_run_defrag_inode(stru
goto cleanup;
}

+ if (cur >= i_size_read(inode)) {
+ iput(inode);
+ goto cleanup;
+ }
+
/* do a chunk of defrag */
clear_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
memset(&range, 0, sizeof(range));
range.len = (u64)-1;
- range.start = defrag->last_offset;
+ range.start = cur;

sb_start_write(fs_info->sb);
- num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
+ ret = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
BTRFS_DEFRAG_BATCH);
sb_end_write(fs_info->sb);
- /*
- * if we filled the whole defrag batch, there
- * must be more work to do. Queue this defrag
- * again
- */
- if (num_defrag == BTRFS_DEFRAG_BATCH) {
- defrag->last_offset = range.start;
- btrfs_requeue_inode_defrag(BTRFS_I(inode), defrag);
- } else if (defrag->last_offset && !defrag->cycled) {
- /*
- * we didn't fill our defrag batch, but
- * we didn't start at zero. Make sure we loop
- * around to the start of the file.
- */
- defrag->last_offset = 0;
- defrag->cycled = 1;
- btrfs_requeue_inode_defrag(BTRFS_I(inode), defrag);
- } else {
- kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
- }
-
iput(inode);
- return 0;
+
+ if (ret < 0)
+ goto cleanup;
+
+ cur = max(cur + fs_info->sectorsize, range.start);
+ goto again;
+
cleanup:
kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
return ret;