btrfs: preallocate compression workspaces (f77dd0d6) · Commits · 戴 / test

Preallocate one workspace for each compression type so we can guarantee forward progress in the worst case. A failure cannot be a hard error as we might not use compression at all on the filesystem. If we can't allocate the workspaces later when need them, it might actually deadlock, but in such situation the system has effectively not enough memory to operate properly. Signed-off-by:

David Sterba <dsterba@suse.com>

fs/btrfs/compression.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -761,10 +761,26 @@ void __init btrfs_init_compress(void)
		int i;

		for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
		struct list_head *workspace;

		INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws);
		spin_lock_init(&btrfs_comp_ws[i].ws_lock);
		atomic_set(&btrfs_comp_ws[i].total_ws, 0);
		init_waitqueue_head(&btrfs_comp_ws[i].ws_wait);

		/*
		* Preallocate one workspace for each compression type so
		* we can guarantee forward progress in the worst case
		*/
		workspace = btrfs_compress_op[i]->alloc_workspace();
		if (IS_ERR(workspace)) {
		printk(KERN_WARNING
		"BTRFS: cannot preallocate compression workspace, will try later");
		} else {
		atomic_set(&btrfs_comp_ws[i].total_ws, 1);
		btrfs_comp_ws[i].free_ws = 1;
		list_add(workspace, &btrfs_comp_ws[i].idle_ws);
		}
		}
		}

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