bcachefs: Add buffered IO fallback for userspace

In userspace, we want to be able to switch to buffered IO when we're
dealing with an image on a filesystem/device that doesn't support the
blocksize the filesystem was formatted with.

This plumbs through !opts.direct_io -> FMODE_BUFFERED, which will be
supported by the shim version of blkdev_get_by_path() in -tools, and it
adds a fallback to disable direct IO and retry for userspace.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index 6ee1e7bb5ebaa155d9a7d8200ab98f81ad33eb5f..deef31a617c4e35c0e529a9db84dbbc2e10562b2 100644 (file)
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -662,7 +662,9 @@ int bch2_read_super(const char *path, struct bch_opts *opts,
        struct printbuf err = PRINTBUF;
        __le64 *i;
        int ret;
-
+#ifndef __KERNEL__
+retry:
+#endif
        memset(sb, 0, sizeof(*sb));
        sb->mode        = BLK_OPEN_READ;
        sb->have_bio    = true;
@@ -670,6 +672,11 @@ int bch2_read_super(const char *path, struct bch_opts *opts,
        if (!sb->holder)
                return -ENOMEM;
 
+#ifndef __KERNEL__
+       if (opt_get(*opts, direct_io) == false)
+               sb->mode |= FMODE_BUFFERED;
+#endif
+
        if (!opt_get(*opts, noexcl))
                sb->mode |= BLK_OPEN_EXCL;
 
@@ -754,7 +761,13 @@ int bch2_read_super(const char *path, struct bch_opts *opts,
 
 got_super:
        if (le16_to_cpu(sb->sb->block_size) << 9 <
-           bdev_logical_block_size(sb->bdev)) {
+           bdev_logical_block_size(sb->bdev) &&
+           opt_get(*opts, direct_io)) {
+#ifndef __KERNEL__
+               opt_set(*opts, direct_io, false);
+               bch2_free_super(sb);
+               goto retry;
+#endif
                prt_printf(&err, "block size (%u) smaller than device block size (%u)",
                       le16_to_cpu(sb->sb->block_size) << 9,
                       bdev_logical_block_size(sb->bdev));