On Fri, Aug 20, 2021 at 04:44:26PM +0300, Nikolay Borisov wrote:

On 18.08.21 г. 0:06, Omar Sandoval wrote:

quoted

From: Omar Sandoval <redacted>

The implementation resembles direct I/O: we have to flush any ordered
extents, invalidate the page cache, and do the io tree/delalloc/extent
map/ordered extent dance. From there, we can reuse the compression code
with a minor modification to distinguish the write from writeback. This
also creates inline extents when possible.

Signed-off-by: Omar Sandoval <redacted>

<snip>

quoted

  * Add an entry indicating a block group or device which is pinned by a

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7a0a9c752624..13a0a65c6a43 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c

@@ -103,6 +103,8 @@ struct btrfs_ioctl_encoded_io_args_32 {
 
 #define BTRFS_IOC_ENCODED_READ_32 _IOR(BTRFS_IOCTL_MAGIC, 64, \
 				       struct btrfs_ioctl_encoded_io_args_32)
+#define BTRFS_IOC_ENCODED_WRITE_32 _IOW(BTRFS_IOCTL_MAGIC, 64, \
+					struct btrfs_ioctl_encoded_io_args_32)
 #endif
 
 /* Mask out flags that are inappropriate for the given type of inode. */

@@ -4992,6 +4994,102 @@ static int btrfs_ioctl_encoded_read(struct file *file, void __user *argp,
 	return ret;
 }
 
+static int btrfs_ioctl_encoded_write(struct file *file, void __user *argp,
+				     bool compat)
+{
+	struct btrfs_ioctl_encoded_io_args args;
+	struct iovec iovstack[UIO_FASTIOV];
+	struct iovec *iov = iovstack;
+	struct iov_iter iter;
+	loff_t pos;
+	struct kiocb kiocb;
+	ssize_t ret;
+
+	if (!capable(CAP_SYS_ADMIN)) {
+		ret = -EPERM;
+		goto out_acct;
+	}
+
+	if (!(file->f_mode & FMODE_WRITE)) {
+		ret = -EBADF;
+		goto out_acct;
+	}
+
+	if (compat) {
+#if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
+		struct btrfs_ioctl_encoded_io_args_32 args32;
+
+		if (copy_from_user(&args32, argp, sizeof(args32))) {
+			ret = -EFAULT;
+			goto out_acct;
+		}
+		args.iov = compat_ptr(args32.iov);
+		args.iovcnt = args.iovcnt;
+		memcpy(&args.offset, &args32.offset,
+		       sizeof(args) -
+		       offsetof(struct btrfs_ioctl_encoded_io_args, offset));
+#else
+		return -ENOTTY;
+#endif
+	} else {
+		if (copy_from_user(&args, argp, sizeof(args))) {
+			ret = -EFAULT;
+			goto out_acct;
+		}
+	}
+
+	ret = -EINVAL;
+	if (args.flags != 0)
+		goto out_acct;
+	if (memchr_inv(args.reserved, 0, sizeof(args.reserved)))
+		goto out_acct;
+	if (args.compression == BTRFS_ENCODED_IO_COMPRESSION_NONE &&
+	    args.encryption == BTRFS_ENCODED_IO_ENCRYPTION_NONE)

Do you intend on supporting encrypted data writeout in the future, given
that in btrfs_do_encoded_write EINVAL is returned if the data to be
written is encrypted? If not then this check could be moved earlier to
fail fast.

We probably want to support it at some point in the future, yes.

quoted

@@ -5138,9 +5236,13 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return fsverity_ioctl_measure(file, argp);
 	case BTRFS_IOC_ENCODED_READ:
 		return btrfs_ioctl_encoded_read(file, argp, false);
+	case BTRFS_IOC_ENCODED_WRITE:
+		return btrfs_ioctl_encoded_write(file, argp, false);
 #if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
 	case BTRFS_IOC_ENCODED_READ_32:
 		return btrfs_ioctl_encoded_read(file, argp, true);
+	case BTRFS_IOC_ENCODED_WRITE_32:
+		return btrfs_ioctl_encoded_write(file, argp, true);
 #endif
 	}
 

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 550c34fa0e6d..180f302dee93 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c

@@ -521,9 +521,15 @@ void btrfs_remove_ordered_extent(struct btrfs_inode *btrfs_inode,
 	spin_lock(&btrfs_inode->lock);
 	btrfs_mod_outstanding_extents(btrfs_inode, -1);
 	spin_unlock(&btrfs_inode->lock);
-	if (root != fs_info->tree_root)
-		btrfs_delalloc_release_metadata(btrfs_inode, entry->num_bytes,
-						false);
+	if (root != fs_info->tree_root) {
+		u64 release;
+
+		if (test_bit(BTRFS_ORDERED_ENCODED, &entry->flags))
+			release = entry->disk_num_bytes;
+		else
+			release = entry->num_bytes;
+		btrfs_delalloc_release_metadata(btrfs_inode, release, false);
+	}
 
 	percpu_counter_add_batch(&fs_info->ordered_bytes, -entry->num_bytes,
 				 fs_info->delalloc_batch);

diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index 0feb0c29839e..04588ccad34c 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h

@@ -74,6 +74,8 @@ enum {
 	BTRFS_ORDERED_LOGGED_CSUM,
 	/* We wait for this extent to complete in the current transaction */
 	BTRFS_ORDERED_PENDING,
+	/* RWF_ENCODED I/O */

nit: RWF_ENCODED is no longer, we simply have ioctl-based encoded io. So
this needs to be renamed to avoid confusion for people not necessarily
faimilar with the development history of the feature.

Good catch, thanks.