On Wed, Oct 16, 2019 at 02:10:10PM +0300, Nikolay Borisov wrote:
>
>
> On 15.10.19 г. 21:42 ч., Omar Sandoval wrote:
> > 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 indicate the size of the extent
> > starting from the read position; we don't need to copy 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.
> > - Cases 3 and 4 do not implement repair yet.
> >
> > Signed-off-by: Omar Sandoval <osandov@xxxxxx>
> > ---
> > fs/btrfs/ctree.h | 2 +
> > fs/btrfs/file.c | 12 +-
> > fs/btrfs/inode.c | 462 +++++++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 475 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index 71552b2ca340..3b2aa1c7218c 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -2906,6 +2906,8 @@ int btrfs_run_delalloc_range(struct 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;
> >
> > /* ioctl.c */
> > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> > index 27e5b269e729..51740cee39fc 100644
> > --- a/fs/btrfs/file.c
> > +++ b/fs/btrfs/file.c
> > @@ -390,6 +390,16 @@ int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
> > return 0;
> > }
> >
> > +static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
> > +{
> > + if (iocb->ki_flags & IOCB_ENCODED) {
> > + if (iocb->ki_flags & IOCB_NOWAIT)
> > + return -EOPNOTSUPP;
> > + return btrfs_encoded_read(iocb, iter);
> > + }
> > + return generic_file_read_iter(iocb, iter);
> > +}
> > +
> > /* simple helper to fault in pages and copy. This should go away
> > * and be replaced with calls into generic code.
> > */
> > @@ -3457,7 +3467,7 @@ static int btrfs_file_open(struct inode *inode, struct file *filp)
> >
> > const struct file_operations btrfs_file_operations = {
> > .llseek = btrfs_file_llseek,
> > - .read_iter = generic_file_read_iter,
> > + .read_iter = btrfs_file_read_iter,
> > .splice_read = generic_file_splice_read,
> > .write_iter = btrfs_file_write_iter,
> > .mmap = btrfs_file_mmap,
> > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > index 8bce46122ef7..174d0738d2c9 100644
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -10593,6 +10593,468 @@ void btrfs_set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
> > }
> > }
> >
> > +static int encoded_iov_compression_from_btrfs(struct encoded_iov *encoded,
> > + unsigned int compress_type)
> > +{
> > + switch (compress_type) {
> > + case BTRFS_COMPRESS_NONE:
> > + encoded->compression = ENCODED_IOV_COMPRESSION_NONE;
> > + break;
> > + case BTRFS_COMPRESS_ZLIB:
> > + encoded->compression = ENCODED_IOV_COMPRESSION_ZLIB;
> > + break;
> > + case BTRFS_COMPRESS_LZO:
> > + encoded->compression = ENCODED_IOV_COMPRESSION_LZO;
> > + break;
> > + case BTRFS_COMPRESS_ZSTD:
> > + encoded->compression = ENCODED_IOV_COMPRESSION_ZSTD;
> > + break;
> > + default:
> > + return -EIO;
> > + }
> > + return 0;
> > +}
> > +
> > +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(encoded,
> > + btrfs_file_extent_compression(leaf, item));
> > + if (ret)
> > + goto out;
> > + 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 = -EFBIG;
> > + 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_free_path(path);
> > + path = NULL;
> > + unlock_extent_cached(io_tree, start, lockend, cached_state);
> > + inode_unlock(inode);
> > + *unlocked = true;
> > + if (copy_to_iter(encoded, sizeof(*encoded), iter) == sizeof(*encoded) &&
> > + copy_to_iter(tmp, count, iter) == count)
> > + ret = count;
> > + else
> > + ret = -EFAULT;
> > + 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;
> > + bool uptodate;
> > + bool skip_csum;
> > +};
> > +
> > +static bool btrfs_encoded_read_check_csums(struct btrfs_io_bio *io_bio)
> > +{
> > + 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 offset = 0;
> > +
> > + if (priv->skip_csum)
> > + return true;
> > + 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++) {
> > + int csum_pos;
> > +
> > + csum_pos = BTRFS_BYTES_TO_BLKS(fs_info, offset);
> > + if (__readpage_endio_check(inode, io_bio, csum_pos,
> > + bvec->bv_page, pgoff,
> > + io_bio->logical + offset,
> > + sectorsize))
> > + return false;
> > + offset += sectorsize;
> > + pgoff += sectorsize;
> > + }
> > + }
> > + return true;
> > +}
> > +
> > +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);
> > +
> > + if (bio->bi_status || !btrfs_encoded_read_check_csums(io_bio))
> > + priv->uptodate = false;
> > + if (!atomic_dec_return(&priv->pending))
> > + wake_up(&priv->wait);
> > + btrfs_io_bio_free_csum(io_bio);
> > + bio_put(bio);
> > +}
> > +
> > +static bool btrfs_submit_encoded_read(struct bio *bio)
> > +{
> > + struct btrfs_encoded_read_private *priv = bio->bi_private;
> > + struct inode *inode = priv->inode;
> > + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> > + blk_status_t status;
> > +
> > + atomic_inc(&priv->pending);
> > +
> > + if (!priv->skip_csum) {
> > + status = btrfs_lookup_bio_sums_at_offset(inode, bio,
> > + btrfs_io_bio(bio)->logical,
> > + NULL);
> > + if (status)
> > + goto out;
> > + }
> > +
> > + status = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
> > + if (status)
> > + goto out;
> > +
> > + status = btrfs_map_bio(fs_info, bio, 0, 0);
> > +out:
> > + if (status) {
> > + bio->bi_status = status;
> > + bio_endio(bio);
> > + return false;
> > + }
> > + return true;
> > +}
> > +
> > +static ssize_t btrfs_encoded_read_regular(struct kiocb *iocb,
> > + struct iov_iter *iter,
> > + u64 start, u64 lockend,
> > + struct extent_state **cached_state,
> > + struct block_device *bdev,
> > + 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 btrfs_encoded_read_private priv = {
> > + .inode = inode,
> > + .wait = __WAIT_QUEUE_HEAD_INITIALIZER(priv.wait),
> > + .pending = ATOMIC_INIT(1),
> > + .uptodate = true,
> > + .skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM,
> > + };
> > + struct page **pages;
> > + unsigned long nr_pages, i;
> > + struct bio *bio = NULL;
> > + u64 cur;
> > + size_t page_offset;
> > + ssize_t ret;
> > +
> > + nr_pages = (disk_io_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
> > + 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;
> > + }
> > + }
> > +
> > + i = 0;
> > + cur = 0;
> > + while (cur < disk_io_size) {
> > + size_t bytes = min_t(u64, disk_io_size - cur,
> > + PAGE_SIZE);
> > +
> > + if (!bio) {
> > + bio = btrfs_bio_alloc(offset + cur);
> > + bio_set_dev(bio, bdev);
> > + bio->bi_end_io = btrfs_encoded_read_endio;
> > + bio->bi_private = &priv;
> > + bio->bi_opf = REQ_OP_READ;
> > + btrfs_io_bio(bio)->logical = start + cur;
> > + }
> > +
> > + if (bio_add_page(bio, pages[i], bytes, 0) < bytes) {
> > + bool success;
> > +
> > + success = btrfs_submit_encoded_read(bio);
> > + bio = NULL;
> > + if (!success)
> > + break;
> > + continue;
> > + }
> > + i++;
> > + cur += bytes;
> > + }
> > +
> > + if (bio)
> > + btrfs_submit_encoded_read(bio);
> > + if (atomic_dec_return(&priv.pending))
> > + wait_event(priv.wait, !atomic_read(&priv.pending));
> > + if (!priv.uptodate) {
> > + ret = -EIO;
> > + goto out;
> > + }
> > +
> > + unlock_extent_cached(io_tree, start, lockend, cached_state);
> > + inode_unlock(inode);
> > + *unlocked = true;
> > +
> > + if (copy_to_iter(encoded, sizeof(*encoded), iter) != sizeof(*encoded)) {
> > + ret = -EFAULT;
> > + 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])
> > + put_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;
> > + struct block_device *em_bdev;
> > + 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 = check_encoded_read(iocb, iter);
> > + if (ret < 0)
> > + return ret;
> > + if (ret == 0) {
> > +empty:
> > + if (copy_to_iter(&encoded, sizeof(encoded), iter) ==
> > + sizeof(encoded))
> > + return 0;
> > + else
> > + return -EFAULT;
>
> nit: Just put the label at the end of the function since it's a simple
> error handler.
It's not really an error handler, it's a corner case. It doesn't seem
any nicer to have the corner case far away at the end of the function
and goto it from two places.
> > + }
> > + count = ret;
> > +
> > + file_accessed(iocb->ki_filp);
> > +
> > + inode_lock(inode);
> > +
> > + if (iocb->ki_pos >= inode->i_size) {
> > + inode_unlock(inode);
> > + goto empty;
>
> That way you won't have to jump backwards here ...
>
> > + }
> > + 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();
> > + }
> > +
> > + em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start,
> > + lockend - start + 1, 0);
> > + if (IS_ERR(em)) {
> > + ret = PTR_ERR(em);
> > + goto out_unlock_extent;
> > + }
> > + em_bdev = em->bdev;
> > +
> > + if (em->block_start == EXTENT_MAP_INLINE) {
> > + u64 extent_start = em->start;
> > +
> > + /*
> > + * For inline extents we get everything we need out of the
> > + * extent item.
> > + */
> > + free_extent_map(em);
> > + em = NULL;
> > + ret = btrfs_encoded_read_inline(iocb, iter, start, lockend,
> > + &cached_state, extent_start,
> > + count, &encoded, &unlocked);
> > + goto out;
> > + }
> > +
> > + /*
> > + * We only want to return up to EOF even if the extent extends beyond
> > + * that.
> > + */
> > + encoded.len = (min_t(u64, extent_map_end(em), inode->i_size) -
> > + iocb->ki_pos);
> > + if (em->block_start == EXTENT_MAP_HOLE ||
> > + test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
> > + offset = EXTENT_MAP_HOLE;
> > + } else if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
> > + offset = em->block_start;
> > + /*
> > + * Bail if the buffer isn't large enough to return the whole
> > + * compressed extent.
> > + */
> > + if (em->block_len > count) {
> > + ret = -EFBIG;
> > + goto out_em;
> > + }
> > + disk_io_size = count = em->block_len;
> > + encoded.unencoded_len = em->ram_bytes;
> > + encoded.unencoded_offset = iocb->ki_pos - em->orig_start;
> > + ret = encoded_iov_compression_from_btrfs(&encoded,
> > + em->compress_type);
> > + if (ret)
> > + goto out_em;
> > + } else {
> > + offset = em->block_start + (start - em->start);
> > + if (encoded.len > count)
> > + encoded.len = count;
> > + /*
> > + * Don't read beyond what we locked. This also limits the page
> > + * allocations that we'll do.
> > + */
> > + disk_io_size = min(lockend + 1, iocb->ki_pos + encoded.len) - start;
> > + encoded.len = encoded.unencoded_len = count =
> > + start + disk_io_size - iocb->ki_pos;
> > + disk_io_size = ALIGN(disk_io_size, fs_info->sectorsize);
> > + }
> > + free_extent_map(em);
> > + em = NULL;
> > +
> > + if (offset == EXTENT_MAP_HOLE) {
> > + unlock_extent_cached(io_tree, start, lockend, &cached_state);
> > + inode_unlock(inode);
> > + unlocked = true;
> > + if (copy_to_iter(&encoded, sizeof(encoded), iter) ==
> > + sizeof(encoded))
> > + ret = 0;
> > + else
> > + ret = -EFAULT;
> > + } else {
> > + ret = btrfs_encoded_read_regular(iocb, iter, start, lockend,
> > + &cached_state, em_bdev, offset,
> > + disk_io_size, count, &encoded,
> > + &unlocked);
> > + }
> > +
> > +out:
> > + if (ret >= 0)
> > + iocb->ki_pos += encoded.len;
> > +out_em:
> > + free_extent_map(em);
> > +out_unlock_extent:
> > + if (!unlocked)
> > + unlock_extent_cached(io_tree, start, lockend, &cached_state);
> > +out_unlock_inode:
> > + if (!unlocked)
> > + inode_unlock(inode);
> > + return ret;
> > +}
> > +
> > #ifdef CONFIG_SWAP
> > /*
> > * Add an entry indicating a block group or device which is pinned by a
> >
