btrfs: allow read-write for 4K sectorsize on 64K page size systems
Since now we support data and metadata read-write for subpage, remove
the RO requirement for subpage mount.
There are some extra limitations though:
- For now, subpage RW mount is still considered experimental
Thus that mount warning will still be there.
- No compression support
There are still quite some PAGE_SIZE hard coded and quite some call
sites use extent_clear_unlock_delalloc() to unlock locked_page.
This will screw up subpage helpers.
Now for subpage RW mount, no matter what mount option or inode attr is
set, all writes will not be compressed. Although reading compressed
data has no problem.
- No defrag for subpage case
The defrag support for subpage case will come in later patches, which
will also rework the defrag workflow.
- No inline extent will be created
This is mostly due to the fact that filemap_fdatawrite_range() will
trigger more write than the range specified.
In fallocate calls, this behavior can make us to writeback which can
be inlined, before we enlarge the i_size.
This is a very special corner case, and even current btrfs check won't
report error on such inline extent + regular extent.
But considering how much effort has been put to prevent such inline +
regular, I'd prefer to cut off inline extent completely until we have
a good solution.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b9ba244..2f9515d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3392,15 +3392,10 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
goto fail_alloc;
}
- /* For 4K sector size support, it's only read-only */
- if (PAGE_SIZE == SZ_64K && sectorsize == SZ_4K) {
- if (!sb_rdonly(sb) || btrfs_super_log_root(disk_super)) {
- btrfs_err(fs_info,
- "subpage sectorsize %u only supported read-only for page size %lu",
- sectorsize, PAGE_SIZE);
- err = -EINVAL;
- goto fail_alloc;
- }
+ if (sectorsize != PAGE_SIZE) {
+ btrfs_warn(fs_info,
+ "read-write for sector size %u with page size %lu is experimental",
+ sectorsize, PAGE_SIZE);
}
if (sectorsize != PAGE_SIZE) {
if (btrfs_super_incompat_flags(fs_info->super_copy) &