From: Omar Sandoval <osandov@xxxxxx>
There are 4 main cases:
1. Inline extents: we copy the data straight out of the extent buffer.
2. Hole/preallocated extents: we fill in zeroes.
3. Regular, uncompressed extents: we read the sectors we need directly
from disk.
4. Regular, compressed extents: we read the entire compressed extent
from disk and indicate what subset of the decompressed extent is in
the file.
This initial implementation simplifies a few things that can be improved
in the future:
- We hold the inode lock during the operation.
- Cases 1, 3, and 4 allocate temporary memory to read into before
copying out to userspace.
- We don't do read repair, because it turns out that read repair is
currently broken for compressed data.
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
---
fs/btrfs/ctree.h | 2 +
fs/btrfs/file.c | 5 +
fs/btrfs/inode.c | 496 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 503 insertions(+)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 6ab2ab002bf6..ce78424f1d98 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3133,6 +3133,8 @@ int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page
int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end);
void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start,
u64 end, int uptodate);
+ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter);
+
extern const struct dentry_operations btrfs_dentry_operations;
extern const struct iomap_ops btrfs_dio_iomap_ops;
extern const struct iomap_dio_ops btrfs_dio_ops;
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 224295f8f1e1..193477565200 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -3629,6 +3629,11 @@ static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
ssize_t ret = 0;
+ if (iocb->ki_flags & IOCB_ENCODED) {
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ return -EOPNOTSUPP;
+ return btrfs_encoded_read(iocb, to);
+ }
if (iocb->ki_flags & IOCB_DIRECT) {
ret = btrfs_direct_read(iocb, to);
if (ret < 0 || !iov_iter_count(to) ||
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 1ff903f5c5a4..b0e800897b3b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9936,6 +9936,502 @@ void btrfs_set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
}
}
+static int encoded_iov_compression_from_btrfs(unsigned int compress_type)
+{
+ switch (compress_type) {
+ case BTRFS_COMPRESS_NONE:
+ return ENCODED_IOV_COMPRESSION_NONE;
+ case BTRFS_COMPRESS_ZLIB:
+ return ENCODED_IOV_COMPRESSION_BTRFS_ZLIB;
+ case BTRFS_COMPRESS_LZO:
+ /*
+ * The LZO format depends on the page size. 64k is the maximum
+ * sectorsize (and thus page size) that we support.
+ */
+ if (PAGE_SIZE < SZ_4K || PAGE_SIZE > SZ_64K)
+ return -EINVAL;
+ return ENCODED_IOV_COMPRESSION_BTRFS_LZO_4K + (PAGE_SHIFT - 12);
+ case BTRFS_COMPRESS_ZSTD:
+ return ENCODED_IOV_COMPRESSION_BTRFS_ZSTD;
+ default:
+ return -EUCLEAN;
+ }
+}
+
+static ssize_t btrfs_encoded_read_inline(struct kiocb *iocb,
+ struct iov_iter *iter, u64 start,
+ u64 lockend,
+ struct extent_state **cached_state,
+ u64 extent_start, size_t count,
+ struct encoded_iov *encoded,
+ bool *unlocked)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+ struct btrfs_path *path;
+ struct extent_buffer *leaf;
+ struct btrfs_file_extent_item *item;
+ u64 ram_bytes;
+ unsigned long ptr;
+ void *tmp;
+ ssize_t ret;
+
+ path = btrfs_alloc_path();
+ if (!path) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root, path,
+ btrfs_ino(BTRFS_I(inode)), extent_start,
+ 0);
+ if (ret) {
+ if (ret > 0) {
+ /* The extent item disappeared? */
+ ret = -EIO;
+ }
+ goto out;
+ }
+ leaf = path->nodes[0];
+ item = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_file_extent_item);
+
+ ram_bytes = btrfs_file_extent_ram_bytes(leaf, item);
+ ptr = btrfs_file_extent_inline_start(item);
+
+ encoded->len = (min_t(u64, extent_start + ram_bytes, inode->i_size) -
+ iocb->ki_pos);
+ ret = encoded_iov_compression_from_btrfs(
+ btrfs_file_extent_compression(leaf, item));
+ if (ret < 0)
+ goto out;
+ encoded->compression = ret;
+ if (encoded->compression) {
+ size_t inline_size;
+
+ inline_size = btrfs_file_extent_inline_item_len(leaf,
+ btrfs_item_nr(path->slots[0]));
+ if (inline_size > count) {
+ ret = -ENOBUFS;
+ goto out;
+ }
+ count = inline_size;
+ encoded->unencoded_len = ram_bytes;
+ encoded->unencoded_offset = iocb->ki_pos - extent_start;
+ } else {
+ encoded->len = encoded->unencoded_len = count =
+ min_t(u64, count, encoded->len);
+ ptr += iocb->ki_pos - extent_start;
+ }
+
+ tmp = kmalloc(count, GFP_NOFS);
+ if (!tmp) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ read_extent_buffer(leaf, tmp, ptr, count);
+ btrfs_release_path(path);
+ unlock_extent_cached(io_tree, start, lockend, cached_state);
+ inode_unlock_shared(inode);
+ *unlocked = true;
+
+ ret = copy_encoded_iov_to_iter(encoded, iter);
+ if (ret)
+ goto out_free;
+ ret = copy_to_iter(tmp, count, iter);
+ if (ret != count)
+ ret = -EFAULT;
+out_free:
+ kfree(tmp);
+out:
+ btrfs_free_path(path);
+ return ret;
+}
+
+struct btrfs_encoded_read_private {
+ struct inode *inode;
+ wait_queue_head_t wait;
+ atomic_t pending;
+ blk_status_t status;
+ bool skip_csum;
+};
+
+static blk_status_t submit_encoded_read_bio(struct inode *inode,
+ struct bio *bio, int mirror_num,
+ unsigned long bio_flags)
+{
+ struct btrfs_encoded_read_private *priv = bio->bi_private;
+ struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ blk_status_t ret;
+
+ if (!priv->skip_csum) {
+ ret = btrfs_lookup_bio_sums(inode, bio, io_bio->logical, NULL);
+ if (ret)
+ return ret;
+ }
+
+ ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
+ if (ret) {
+ btrfs_io_bio_free_csum(io_bio);
+ return ret;
+ }
+
+ atomic_inc(&priv->pending);
+ ret = btrfs_map_bio(fs_info, bio, mirror_num);
+ if (ret) {
+ atomic_dec(&priv->pending);
+ btrfs_io_bio_free_csum(io_bio);
+ }
+ return ret;
+}
+
+static blk_status_t btrfs_encoded_read_check_bio(struct btrfs_io_bio *io_bio)
+{
+ const bool uptodate = io_bio->bio.bi_status == BLK_STS_OK;
+ struct btrfs_encoded_read_private *priv = io_bio->bio.bi_private;
+ struct inode *inode = priv->inode;
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ u32 sectorsize = fs_info->sectorsize;
+ struct bio_vec *bvec;
+ struct bvec_iter_all iter_all;
+ u64 start = io_bio->logical;
+ int icsum = 0;
+
+ if (priv->skip_csum || !uptodate)
+ return io_bio->bio.bi_status;
+
+ bio_for_each_segment_all(bvec, &io_bio->bio, iter_all) {
+ unsigned int i, nr_sectors, pgoff;
+
+ nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec->bv_len);
+ pgoff = bvec->bv_offset;
+ for (i = 0; i < nr_sectors; i++) {
+ ASSERT(pgoff < PAGE_SIZE);
+ if (check_data_csum(inode, io_bio, icsum, bvec->bv_page,
+ pgoff, start))
+ return BLK_STS_IOERR;
+ start += sectorsize;
+ icsum++;
+ pgoff += sectorsize;
+ }
+ }
+ return BLK_STS_OK;
+}
+
+static void btrfs_encoded_read_endio(struct bio *bio)
+{
+ struct btrfs_encoded_read_private *priv = bio->bi_private;
+ struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
+ blk_status_t status;
+
+ status = btrfs_encoded_read_check_bio(io_bio);
+ if (status) {
+ /*
+ * The memory barrier implied by the atomic_dec_return() here
+ * pairs with the memory barrier implied by the
+ * atomic_dec_return() or io_wait_event() in
+ * btrfs_encoded_read_regular_fill_pages() to ensure that this
+ * write is observed before the load of status in
+ * btrfs_encoded_read_regular_fill_pages().
+ */
+ WRITE_ONCE(priv->status, status);
+ }
+ if (!atomic_dec_return(&priv->pending))
+ wake_up(&priv->wait);
+ btrfs_io_bio_free_csum(io_bio);
+ bio_put(bio);
+}
+
+static int btrfs_encoded_read_regular_fill_pages(struct inode *inode, u64 offset,
+ u64 disk_io_size, struct page **pages)
+{
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ struct btrfs_encoded_read_private priv = {
+ .inode = inode,
+ .pending = ATOMIC_INIT(1),
+ .skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM,
+ };
+ unsigned long i = 0;
+ u64 cur = 0;
+ int ret;
+
+ init_waitqueue_head(&priv.wait);
+ /*
+ * Submit bios for the extent, splitting due to bio or stripe limits as
+ * necessary.
+ */
+ while (cur < disk_io_size) {
+ struct btrfs_io_geometry geom;
+ struct bio *bio = NULL;
+ u64 remaining;
+
+ ret = btrfs_get_io_geometry(fs_info, BTRFS_MAP_READ,
+ offset + cur, disk_io_size - cur,
+ &geom);
+ if (ret) {
+ WRITE_ONCE(priv.status, errno_to_blk_status(ret));
+ break;
+ }
+ remaining = min(geom.len, disk_io_size - cur);
+ while (bio || remaining) {
+ size_t bytes = min_t(u64, remaining, PAGE_SIZE);
+
+ if (!bio) {
+ bio = btrfs_bio_alloc(offset + cur);
+ bio->bi_end_io = btrfs_encoded_read_endio;
+ bio->bi_private = &priv;
+ bio->bi_opf = REQ_OP_READ;
+ }
+
+ if (!bytes ||
+ bio_add_page(bio, pages[i], bytes, 0) < bytes) {
+ blk_status_t status;
+
+ status = submit_encoded_read_bio(inode, bio, 0,
+ 0);
+ if (status) {
+ WRITE_ONCE(priv.status, status);
+ bio_put(bio);
+ goto out;
+ }
+ bio = NULL;
+ continue;
+ }
+
+ i++;
+ cur += bytes;
+ remaining -= bytes;
+ }
+ }
+
+out:
+ if (atomic_dec_return(&priv.pending))
+ io_wait_event(priv.wait, !atomic_read(&priv.pending));
+ /* See btrfs_encoded_read_endio() for ordering. */
+ return blk_status_to_errno(READ_ONCE(priv.status));
+}
+
+static ssize_t btrfs_encoded_read_regular(struct kiocb *iocb,
+ struct iov_iter *iter,
+ u64 start, u64 lockend,
+ struct extent_state **cached_state,
+ u64 offset, u64 disk_io_size,
+ size_t count,
+ const struct encoded_iov *encoded,
+ bool *unlocked)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+ struct page **pages;
+ unsigned long nr_pages, i;
+ u64 cur;
+ size_t page_offset;
+ ssize_t ret;
+
+ nr_pages = DIV_ROUND_UP(disk_io_size, PAGE_SIZE);
+ pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
+ if (!pages)
+ return -ENOMEM;
+ for (i = 0; i < nr_pages; i++) {
+ pages[i] = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+ if (!pages[i]) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ }
+
+ ret = btrfs_encoded_read_regular_fill_pages(inode, offset, disk_io_size,
+ pages);
+ if (ret)
+ goto out;
+
+ unlock_extent_cached(io_tree, start, lockend, cached_state);
+ inode_unlock_shared(inode);
+ *unlocked = true;
+
+ ret = copy_encoded_iov_to_iter(encoded, iter);
+ if (ret)
+ goto out;
+ if (encoded->compression) {
+ i = 0;
+ page_offset = 0;
+ } else {
+ i = (iocb->ki_pos - start) >> PAGE_SHIFT;
+ page_offset = (iocb->ki_pos - start) & (PAGE_SIZE - 1);
+ }
+ cur = 0;
+ while (cur < count) {
+ size_t bytes = min_t(size_t, count - cur,
+ PAGE_SIZE - page_offset);
+
+ if (copy_page_to_iter(pages[i], page_offset, bytes,
+ iter) != bytes) {
+ ret = -EFAULT;
+ goto out;
+ }
+ i++;
+ cur += bytes;
+ page_offset = 0;
+ }
+ ret = count;
+out:
+ for (i = 0; i < nr_pages; i++) {
+ if (pages[i])
+ __free_page(pages[i]);
+ }
+ kfree(pages);
+ return ret;
+}
+
+ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+ ssize_t ret;
+ size_t count;
+ u64 start, lockend, offset, disk_io_size;
+ struct extent_state *cached_state = NULL;
+ struct extent_map *em;
+ struct encoded_iov encoded = {};
+ bool unlocked = false;
+
+ ret = generic_encoded_read_checks(iocb, iter);
+ if (ret < 0)
+ return ret;
+ if (ret == 0)
+ return copy_encoded_iov_to_iter(&encoded, iter);
+ count = ret;
+
+ file_accessed(iocb->ki_filp);
+
+ inode_lock_shared(inode);
+
+ if (iocb->ki_pos >= inode->i_size) {
+ inode_unlock_shared(inode);
+ return copy_encoded_iov_to_iter(&encoded, iter);
+ }
+ start = ALIGN_DOWN(iocb->ki_pos, fs_info->sectorsize);
+ /*
+ * We don't know how long the extent containing iocb->ki_pos is, but if
+ * it's compressed we know that it won't be longer than this.
+ */
+ lockend = start + BTRFS_MAX_UNCOMPRESSED - 1;
+
+ for (;;) {
+ struct btrfs_ordered_extent *ordered;
+
+ ret = btrfs_wait_ordered_range(inode, start,
+ lockend - start + 1);
+ if (ret)
+ goto out_unlock_inode;
+ lock_extent_bits(io_tree, start, lockend, &cached_state);
+ ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start,
+ lockend - start + 1);
+ if (!ordered)
+ break;
+ btrfs_put_ordered_extent(ordered);
+ unlock_extent_cached(io_tree, start, lockend, &cached_state);
+ cond_resched();
+ }
