[PATCH 5/5] btrfs: add io_uring command for encoded reads

Mark Harmstone
2024-10-22T14:50:53Z

Adds an io_uring command for encoded reads, using the same interface as
the existing BTRFS_IOC_ENCODED_READ ioctl.

btrfs_uring_encoded_read is an io_uring version of
btrfs_ioctl_encoded_read, which validates the user input and calls
btrfs_encoded_read to read the appropriate metadata. If we determine
that we need to read an extent from disk, we call
btrfs_encoded_read_regular_fill_pages through btrfs_uring_read_extent to
prepare the bio.

The existing btrfs_encoded_read_regular_fill_pages is changed so that if
it is passed a uring_ctx value, rather than waking up any waiting
threads it calls btrfs_uring_read_extent_endio. This in turn copies the
read data back to userspace, and calls io_uring_cmd_done to complete the
io_uring command.

Because we're potentially doing a non-blocking read,
btrfs_uring_read_extent doesn't clean up after itself if it returns
-EIOCBQUEUED. Instead, it allocates a priv struct, populates the fields
there that we will need to unlock the inode and free our allocations,
and defers this to the btrfs_uring_read_finished that gets called when
the bio completes.

Signed-off-by: Mark Harmstone <maharmstone@fb.com>
---
fs/btrfs/btrfs_inode.h | 3 +-
fs/btrfs/file.c | 1 +
fs/btrfs/inode.c | 43 ++++--
fs/btrfs/ioctl.c | 309 +++++++++++++++++++++++++++++++++++++++++
fs/btrfs/ioctl.h | 2 +
fs/btrfs/send.c | 3 +-
6 files changed, 349 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index ab1fbde97cee..f551444b498e 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -613,7 +613,8 @@ int btrfs_encoded_io_compression_from_extent(struct btrfs_fs_info *fs_info,
int compress_type);
int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
u64 disk_bytenr, u64 disk_io_size,
- struct page **pages);
+ struct page **pages,
+ void *uring_ctx);
ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
struct btrfs_ioctl_encoded_io_args *encoded,
struct extent_state **cached_state,
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 5e0a1805e897..fbb753300071 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -3710,6 +3710,7 @@ const struct file_operations btrfs_file_operations = {
.compat_ioctl = btrfs_compat_ioctl,
#endif
.remap_file_range = btrfs_remap_file_range,
+ .uring_cmd = btrfs_uring_cmd,
.fop_flags = FOP_BUFFER_RASYNC | FOP_BUFFER_WASYNC,
};

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5aedb85696f4..759ae076f90b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9057,6 +9057,7 @@ static ssize_t btrfs_encoded_read_inline(

struct btrfs_encoded_read_private {
wait_queue_head_t wait;
+ void *uring_ctx;
atomic_t pending;
blk_status_t status;
};
@@ -9076,14 +9077,23 @@ static void btrfs_encoded_read_endio(struct btrfs_bio *bbio)
*/
WRITE_ONCE(priv->status, bbio->bio.bi_status);
}
- if (!atomic_dec_return(&priv->pending))
- wake_up(&priv->wait);
+ if (atomic_dec_return(&priv->pending) == 0) {
+ int err = blk_status_to_errno(READ_ONCE(priv->status));
+
+ if (priv->uring_ctx) {
+ btrfs_uring_read_extent_endio(priv->uring_ctx, err);
+ kfree(priv);
+ } else {
+ wake_up(&priv->wait);
+ }
+ }
bio_put(&bbio->bio);
}

int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
u64 disk_bytenr, u64 disk_io_size,
- struct page **pages)
+ struct page **pages,
+ void *uring_ctx)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
struct btrfs_encoded_read_private *priv;
@@ -9098,6 +9108,7 @@ int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
init_waitqueue_head(&priv->wait);
atomic_set(&priv->pending, 1);
priv->status = 0;
+ priv->uring_ctx = uring_ctx;

bbio = btrfs_bio_alloc(BIO_MAX_VECS, REQ_OP_READ, fs_info,
btrfs_encoded_read_endio, priv);
@@ -9126,12 +9137,23 @@ int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
atomic_inc(&priv->pending);
btrfs_submit_bbio(bbio, 0);

- if (atomic_dec_return(&priv->pending))
- io_wait_event(priv->wait, !atomic_read(&priv->pending));
- /* See btrfs_encoded_read_endio() for ordering. */
- ret = blk_status_to_errno(READ_ONCE(priv->status));
- kfree(priv);
- return ret;
+ if (uring_ctx) {
+ if (atomic_dec_return(&priv->pending) == 0) {
+ ret = blk_status_to_errno(READ_ONCE(priv->status));
+ btrfs_uring_read_extent_endio(uring_ctx, ret);
+ kfree(priv);
+ return ret;
+ }
+
+ return -EIOCBQUEUED;
+ } else {
+ if (atomic_dec_return(&priv->pending) != 0)
+ io_wait_event(priv->wait, !atomic_read(&priv->pending));
+ /* See btrfs_encoded_read_endio() for ordering. */
+ ret = blk_status_to_errno(READ_ONCE(priv->status));
+ kfree(priv);
+ return ret;
+ }
}

ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, struct iov_iter *iter,
@@ -9160,7 +9182,8 @@ ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, struct iov_iter *iter,
}

ret = btrfs_encoded_read_regular_fill_pages(inode, disk_bytenr,
- disk_io_size, pages);
+ disk_io_size, pages,
+ NULL);
if (ret)
goto out;

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d502b31010bc..7f2731ef3dbb 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -29,6 +29,7 @@
#include <linux/fileattr.h>
#include <linux/fsverity.h>
#include <linux/sched/xacct.h>
+#include <linux/io_uring/cmd.h>
#include "ctree.h"
#include "disk-io.h"
#include "export.h"
@@ -4720,6 +4721,314 @@ static int btrfs_ioctl_encoded_write(struct file *file, void __user *argp, bool
return ret;
}

+/*
+ * struct btrfs_uring_priv is the context that's attached to an encoded read
+ * io_uring command, in cmd->pdu. It contains the fields in
+ * btrfs_uring_read_extent that are necessary to finish off and cleanup the I/O
+ * in btrfs_uring_read_finished.
+ */
+struct btrfs_uring_priv {
+ struct io_uring_cmd *cmd;
+ struct page **pages;
+ unsigned long nr_pages;
+ struct kiocb iocb;
+ struct iovec *iov;
+ struct iov_iter iter;
+ struct extent_state *cached_state;
+ u64 count;
+ u64 start;
+ u64 lockend;
+ int err;
+ bool compressed;
+};
+
+static void btrfs_uring_read_finished(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
+{
+ struct btrfs_uring_priv *priv =
+ *io_uring_cmd_to_pdu(cmd, struct btrfs_uring_priv *);
+ struct btrfs_inode *inode = BTRFS_I(file_inode(priv->iocb.ki_filp));
+ struct extent_io_tree *io_tree = &inode->io_tree;
+ unsigned long i;
+ u64 cur;
+ size_t page_offset;
+ ssize_t ret;
+
+ if (priv->err) {
+ ret = priv->err;
+ goto out;
+ }
+
+ if (priv->compressed) {
+ i = 0;
+ page_offset = 0;
+ } else {
+ i = (priv->iocb.ki_pos - priv->start) >> PAGE_SHIFT;
+ page_offset = offset_in_page(priv->iocb.ki_pos - priv->start);
+ }
+ cur = 0;
+ while (cur < priv->count) {
+ size_t bytes = min_t(size_t, priv->count - cur,
+ PAGE_SIZE - page_offset);
+
+ if (copy_page_to_iter(priv->pages[i], page_offset, bytes,
+ &priv->iter) != bytes) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ i++;
+ cur += bytes;
+ page_offset = 0;
+ }
+ ret = priv->count;
+
+out:
+ unlock_extent(io_tree, priv->start, priv->lockend, &priv->cached_state);
+ btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
+
+ io_uring_cmd_done(cmd, ret, 0, issue_flags);
+ add_rchar(current, ret);
+
+ for (unsigned long index = 0; index < priv->nr_pages; index++)
+ __free_page(priv->pages[index]);
+
+ kfree(priv->pages);
+ kfree(priv->iov);
+ kfree(priv);
+}
+
+void btrfs_uring_read_extent_endio(void *ctx, int err)
+{
+ struct btrfs_uring_priv *priv = ctx;
+
+ priv->err = err;
+
+ *io_uring_cmd_to_pdu(priv->cmd, struct btrfs_uring_priv *) = priv;
+ io_uring_cmd_complete_in_task(priv->cmd, btrfs_uring_read_finished);
+}
+
+static int btrfs_uring_read_extent(struct kiocb *iocb, struct iov_iter *iter,
+ u64 start, u64 lockend,
+ struct extent_state *cached_state,
+ u64 disk_bytenr, u64 disk_io_size,
+ size_t count, bool compressed,
+ struct iovec *iov,
+ struct io_uring_cmd *cmd)
+{
+ struct btrfs_inode *inode = BTRFS_I(file_inode(iocb->ki_filp));
+ struct extent_io_tree *io_tree = &inode->io_tree;
+ struct page **pages;
+ struct btrfs_uring_priv *priv = NULL;
+ unsigned long nr_pages;
+ int ret;
+
+ nr_pages = DIV_ROUND_UP(disk_io_size, PAGE_SIZE);
+ pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
+ if (!pages)
+ return -ENOMEM;
+ ret = btrfs_alloc_page_array(nr_pages, pages, 0);
+ if (ret) {
+ ret = -ENOMEM;
+ goto fail;
+ }
+
+ priv = kmalloc(sizeof(*priv), GFP_NOFS);
+ if (!priv) {
+ ret = -ENOMEM;
+ goto fail;
+ }
+
+ priv->iocb = *iocb;
+ priv->iov = iov;
+ priv->iter = *iter;
+ priv->count = count;
+ priv->cmd = cmd;
+ priv->cached_state = cached_state;
+ priv->compressed = compressed;
+ priv->nr_pages = nr_pages;
+ priv->pages = pages;
+ priv->start = start;
+ priv->lockend = lockend;
+ priv->err = 0;
+
+ ret = btrfs_encoded_read_regular_fill_pages(inode, disk_bytenr,
+ disk_io_size, pages,
+ priv);
+ if (ret && ret != -EIOCBQUEUED)
+ goto fail;
+
+ /*
+ * If we return -EIOCBQUEUED, we're deferring the cleanup to
+ * btrfs_uring_read_finished, which will handle unlocking the extent
+ * and inode and freeing the allocations.
+ */
+
+ return -EIOCBQUEUED;
+
+fail:
+ unlock_extent(io_tree, start, lockend, &cached_state);
+ btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
+ kfree(priv);
+ return ret;
+}
+
+static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
+{
+ size_t copy_end_kernel = offsetofend(struct btrfs_ioctl_encoded_io_args,
+ flags);
+ size_t copy_end;
+ struct btrfs_ioctl_encoded_io_args args = { 0 };
+ int ret;
+ u64 disk_bytenr, disk_io_size;
+ struct file *file = cmd->file;
+ struct btrfs_inode *inode = BTRFS_I(file->f_inode);
+ struct btrfs_fs_info *fs_info = inode->root->fs_info;
+ struct extent_io_tree *io_tree = &inode->io_tree;
+ struct iovec iovstack[UIO_FASTIOV];
+ struct iovec *iov = iovstack;
+ struct iov_iter iter;
+ loff_t pos;
+ struct kiocb kiocb;
+ struct extent_state *cached_state = NULL;
+ u64 start, lockend;
+ void __user *sqe_addr = u64_to_user_ptr(READ_ONCE(cmd->sqe->addr));
+
+ if (!capable(CAP_SYS_ADMIN)) {
+ ret = -EPERM;
+ goto out_acct;
+ }
+
+ if (issue_flags & IO_URING_F_COMPAT) {
+#if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
+ struct btrfs_ioctl_encoded_io_args_32 args32;
+
+ copy_end = offsetofend(struct btrfs_ioctl_encoded_io_args_32,
+ flags);
+ if (copy_from_user(&args32, sqe_addr, copy_end)) {
+ ret = -EFAULT;
+ goto out_acct;
+ }
+ args.iov = compat_ptr(args32.iov);
+ args.iovcnt = args32.iovcnt;
+ args.offset = args32.offset;
+ args.flags = args32.flags;
+#else
+ return -ENOTTY;
+#endif
+ } else {
+ copy_end = copy_end_kernel;
+ if (copy_from_user(&args, sqe_addr, copy_end)) {
+ ret = -EFAULT;
+ goto out_acct;
+ }
+ }
+
+ if (args.flags != 0)
+ return -EINVAL;
+
+ ret = import_iovec(ITER_DEST, args.iov, args.iovcnt, ARRAY_SIZE(iovstack),
+ &iov, &iter);
+ if (ret < 0)
+ goto out_acct;
+
+ if (iov_iter_count(&iter) == 0) {
+ ret = 0;
+ goto out_free;
+ }
+
+ pos = args.offset;
+ ret = rw_verify_area(READ, file, &pos, args.len);
+ if (ret < 0)
+ goto out_free;
+
+ init_sync_kiocb(&kiocb, file);
+ kiocb.ki_pos = pos;
+
+ if (issue_flags & IO_URING_F_NONBLOCK)
+ kiocb.ki_flags |= IOCB_NOWAIT;
+
+ start = ALIGN_DOWN(pos, fs_info->sectorsize);
+ lockend = start + BTRFS_MAX_UNCOMPRESSED - 1;
+
+ ret = btrfs_encoded_read(&kiocb, &iter, &args, &cached_state,
+ &disk_bytenr, &disk_io_size);
+ if (ret < 0 && ret != -EIOCBQUEUED)
+ goto out_free;
+
+ file_accessed(file);
+
+ if (copy_to_user(sqe_addr + copy_end, (char *)&args + copy_end_kernel,
+ sizeof(args) - copy_end_kernel)) {
+ if (ret == -EIOCBQUEUED) {
+ unlock_extent(io_tree, start, lockend, &cached_state);
+ btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
+ }
+ ret = -EFAULT;
+ goto out_free;
+ }
+
+ if (ret == -EIOCBQUEUED) {
+ u64 count;
+
+ /*
+ * If we've optimized things by storing the iovecs on the stack,
+ * undo this.
+ */
+ if (!iov) {
+ iov = kmalloc(sizeof(struct iovec) * args.iovcnt,
+ GFP_NOFS);
+ if (!iov) {
+ unlock_extent(io_tree, start, lockend,
+ &cached_state);
+ btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
+ ret = -ENOMEM;
+ goto out_acct;
+ }
+
+ memcpy(iov, iovstack,
+ sizeof(struct iovec) * args.iovcnt);
+ }
+
+ count = min_t(u64, iov_iter_count(&iter), disk_io_size);
+
+ /* Match ioctl by not returning past EOF if uncompressed */
+ if (!args.compression)
+ count = min_t(u64, count, args.len);
+
+ ret = btrfs_uring_read_extent(&kiocb, &iter, start, lockend,
+ cached_state, disk_bytenr,
+ disk_io_size, count,
+ args.compression, iov, cmd);
+
+ goto out_acct;
+ }
+
+out_free:
+ kfree(iov);
+
+out_acct:
+ if (ret > 0)
+ add_rchar(current, ret);
+ inc_syscr(current);
+
+ return ret;
+}
+
+int btrfs_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+ switch (cmd->cmd_op) {
+ case BTRFS_IOC_ENCODED_READ:
+#if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
+ case BTRFS_IOC_ENCODED_READ_32:
+#endif
+ return btrfs_uring_encoded_read(cmd, issue_flags);
+ }
+
+ return -EINVAL;
+}
+
long btrfs_ioctl(struct file *file, unsigned int
cmd, unsigned long arg)
{
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 19cd26b0244a..2b760c8778f8 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -22,5 +22,7 @@ void btrfs_sync_inode_flags_to_i_flags(struct inode *inode);
int __pure btrfs_is_empty_uuid(const u8 *uuid);
void btrfs_update_ioctl_balance_args(struct btrfs_fs_info *fs_info,
struct btrfs_ioctl_balance_args *bargs);
+int btrfs_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags);
+void btrfs_uring_read_extent_endio(void *ctx, int err);

#endif
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 03b31b1c39be..cadb945bb345 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -5669,7 +5669,8 @@ static int send_encoded_extent(struct send_ctx *sctx, struct btrfs_path *path,
ret = btrfs_encoded_read_regular_fill_pages(BTRFS_I(inode),
disk_bytenr, disk_num_bytes,
sctx->send_buf_pages +
- (data_offset >> PAGE_SHIFT));
+ (data_offset >> PAGE_SHIFT),
+ NULL);
if (ret)
goto out;

--
2.45.2