From ca62e85ded2c02f5e5d469103f2a5b6b09883dcc Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Mon, 26 Jul 2021 14:34:52 +0800
Patch-mainline: v5.15-rc1
References: jsc#SLE-17681
Git-commit: ca62e85ded2c02f5e5d469103f2a5b6b09883dcc
Subject: [PATCH 03/18] btrfs: disable compressed readahead for subpage
For current subpage support, we only support 64K page size with 4K
sector size.
This makes compressed readahead less effective, as maximum compressed
extent size is only 128K, 2x the page size.
On the other hand, the function add_ra_bio_pages() is still assuming
sectorsize == PAGE_SIZE, and code change may affect 4K page size
systems.
So for now, let's disable subpage compressed readahead for now.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/compression.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index aeda426b6121..18579b904d5c 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -564,6 +564,16 @@ static noinline int add_ra_bio_pages(struct inode *inode,
if (isize == 0)
return 0;
+ /*
+ * For current subpage support, we only support 64K page size,
+ * which means maximum compressed extent size (128K) is just 2x page
+ * size.
+ * This makes readahead less effective, so here disable readahead for
+ * subpage for now, until full compressed write is supported.
+ */
+ if (btrfs_sb(inode->i_sb)->sectorsize < PAGE_SIZE)
+ return 0;
+
end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
while (last_offset < compressed_end) {
--
2.33.0