Btrfs: only map pages if we know we need them when reading the space cache (2f120c05) · Commits · 戴 / test

People have been running into a warning when loading space cache because the page is already mapped when trying to read in a bitmap. The way we read in entries and pages is kind of convoluted, so fix it so that io_ctl_read_entry maps the entries if it needs to, and if it hits the end of the page it simply unmaps the page. That way we can unconditionally unmap the io_ctl before reading in the bitmap and we should stop hitting these warnings. Thanks, Signed-off-by:

Josef Bacik <josef@redhat.com> Signed-off-by:

Chris Mason <chris.mason@oracle.com>

fs/btrfs/free-space-cache.c

+10 −7

Original line number	Diff line number	Diff line
		@@ -537,6 +537,13 @@ static int io_ctl_read_entry(struct io_ctl *io_ctl,
		struct btrfs_free_space entry, u8 type)
		{
		struct btrfs_free_space_entry *e;
		int ret;

		if (!io_ctl->cur) {
		ret = io_ctl_check_crc(io_ctl, io_ctl->index);
		if (ret)
		return ret;
		}

		e = io_ctl->cur;
		entry->offset = le64_to_cpu(e->offset);
		@@ -550,10 +557,7 @@ static int io_ctl_read_entry(struct io_ctl *io_ctl,

		io_ctl_unmap_page(io_ctl);

		if (io_ctl->index >= io_ctl->num_pages)
		return 0;

		return io_ctl_check_crc(io_ctl, io_ctl->index);
		}

		static int io_ctl_read_bitmap(struct io_ctl *io_ctl,
		@@ -561,9 +565,6 @@ static int io_ctl_read_bitmap(struct io_ctl *io_ctl,
		{
		int ret;

		if (io_ctl->cur && io_ctl->cur != io_ctl->orig)
		io_ctl_unmap_page(io_ctl);

		ret = io_ctl_check_crc(io_ctl, io_ctl->index);
		if (ret)
		return ret;
		@@ -699,6 +700,8 @@ int __load_free_space_cache(struct btrfs_root root, struct inode inode,
		num_entries--;
		}

		io_ctl_unmap_page(&io_ctl);

		/*
		* We add the bitmaps at the end of the entries in order that
		* the bitmap entries are added to the cache.

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