[RFC] erofs-utils: on-disk extent format for blocks.
Gao Xiang
hsiangkao at aol.com
Sun Dec 29 13:55:48 AEDT 2019
Hi Pratik,
On Fri, Dec 27, 2019 at 09:13:48PM +0530, Pratik Shinde wrote:
> since this patch is quite different from previous patches I am treating
> this as new patch.
>
> 1) On disk extent format for erofs data blocks.
> 2) Detect holes inside files & skip allocation for hole blocks.
>
> Signed-off-by: Pratik Shinde <pratikshinde320 at gmail.com>
> ---
> include/erofs/internal.h | 21 ++++++-
> lib/inode.c | 155 +++++++++++++++++++++++++++++++++++++++++------
> 2 files changed, 156 insertions(+), 20 deletions(-)
>
> diff --git a/include/erofs/internal.h b/include/erofs/internal.h
> index e13adda..128aa63 100644
> --- a/include/erofs/internal.h
> +++ b/include/erofs/internal.h
> @@ -63,7 +63,7 @@ struct erofs_sb_info {
> extern struct erofs_sb_info sbi;
>
> struct erofs_inode {
> - struct list_head i_hash, i_subdirs, i_xattrs;
> + struct list_head i_hash, i_subdirs, i_xattrs, i_extents;
>
> unsigned int i_count;
> struct erofs_inode *i_parent;
> @@ -93,6 +93,7 @@ struct erofs_inode {
>
> unsigned int xattr_isize;
> unsigned int extent_isize;
> + unsigned int extent_meta_isize;
maybe sparse_extent_isize is better...
p.s. maybe we could send another patch rename extent_isize to
compress_extent_isize or some better name...
>
> erofs_nid_t nid;
> struct erofs_buffer_head *bh;
> @@ -139,5 +140,23 @@ static inline const char *erofs_strerror(int err)
> return msg;
> }
>
> +#define HOLE_BLK -1
> +/* on disk extent format */
> +struct erofs_extent {
> + __le32 ee_lblk;
> + __le32 ee_pblk;
> + __le32 ee_len;
> +};
> +
> +struct erofs_extent_node {
> + struct list_head next;
> + erofs_blk_t lblk;
> + erofs_blk_t pblk;
> + u32 len;
> +};
> +
> +struct erofs_inline_extent_header {
> + u32 count;
> +};
> #endif
>
> diff --git a/lib/inode.c b/lib/inode.c
> index 0e19b11..a6af509 100644
> --- a/lib/inode.c
> +++ b/lib/inode.c
> @@ -38,6 +38,99 @@ static unsigned char erofs_type_by_mode[S_IFMT >> S_SHIFT] = {
>
> struct list_head inode_hashtable[NR_INODE_HASHTABLE];
>
> +
> +#define IS_HOLE(start, end) (roundup(start, EROFS_BLKSIZ) == start && \
> + roundup(end, EROFS_BLKSIZ) == end && \
> + (end - start) % EROFS_BLKSIZ == 0)
See below..
> +
> +/* returns the number of holes present in the file */
> +unsigned int erofs_read_extents(struct erofs_inode *inode,
> + struct list_head *extents)
> +{
> + int fd, st, en, dt;
> + unsigned int nholes = 0;
> + erofs_off_t data, hole, len, last_data;
> + struct erofs_extent_node *e_hole, *e_data;
> +
> + fd = open(inode->i_srcpath, O_RDONLY);
> + if (fd < 0) {
> + return -errno;
> + }
> + len = lseek(fd, 0, SEEK_END);
> + if (lseek(fd, 0, SEEK_SET) == -1)
> + return -errno;
> + data = 0;
> + last_data = 0;
> + while (data < len) {
> + hole = lseek(fd, data, SEEK_HOLE);
> + if (hole == len)
> + break;
> + data = lseek(fd, hole, SEEK_DATA);
> + if (data < 0 || hole > data) {
> + return -EINVAL;
> + }
> + if (IS_HOLE(hole, data)) {
> + st = hole >> S_SHIFT;
> + en = data >> S_SHIFT;
> + dt = last_data >> S_SHIFT;
Why using S_SHIFT here, some special meaning?
> + last_data = data;
> + e_data = malloc(sizeof(struct erofs_extent_node));
> + if (e_data == NULL)
> + return -ENOMEM;
> + e_data->lblk = dt;
> + e_data->len = (st - dt);
> + list_add_tail(&e_data->next, extents);
> + e_hole = malloc(sizeof(struct erofs_extent_node));
> + if (e_hole == NULL)
> + return -ENOMEM;
> + e_hole->lblk = st;
> + e_hole->pblk = HOLE_BLK;
> + e_hole->len = (en - st);
> + list_add_tail(&e_hole->next, extents);
> + nholes += e_hole->len;
Maybe we don't need to emit all HOLK extents since all data extents
are with _length_... It is easy to detect all holes between extents...
If some block doesn't belong to any extent, it's a hole.
Thanks,
Gao Xiang
> + }
> + }
> + /* rounddown to exclude tail-end data */
> + if (last_data < len && (len - last_data) >= EROFS_BLKSIZ) {
> + e_data = malloc(sizeof(struct erofs_extent_node));
> + if (e_data == NULL)
> + return -ENOMEM;
> + st = last_data >> S_SHIFT;
> + e_data->lblk = st;
> + e_data->len = rounddown((len - last_data), EROFS_BLKSIZ) >> S_SHIFT;
> + list_add_tail(&e_data->next, extents);
> + }
> + return nholes;
> +}
> +
> +char *erofs_create_extent_buffer(struct list_head *extents, unsigned int size)
> +{
> + struct erofs_extent_node *e_node;
> + struct erofs_inline_extent_header *header;
> + char *buf;
> + unsigned int p = 0;
> +
> + buf = malloc(size);
> + if (buf == NULL)
> + return ERR_PTR(-ENOMEM);
> + header = (struct erofs_inline_extent_header *) buf;
> + header->count = 0;
> + p += sizeof(struct erofs_inline_extent_header);
> + list_for_each_entry(e_node, extents, next) {
> + const struct erofs_extent ee = {
> + .ee_lblk = cpu_to_le32(e_node->lblk),
> + .ee_pblk = cpu_to_le32(e_node->pblk),
> + .ee_len = cpu_to_le32(e_node->len)
> + };
> + memcpy(buf + p, &ee, sizeof(struct erofs_extent));
> + p += sizeof(struct erofs_extent);
> + header->count++;
> + list_del(&e_node->next);
> + free(e_node);
> + }
> + return buf;
> +}
> +
> void erofs_inode_manager_init(void)
> {
> unsigned int i;
> @@ -304,8 +397,9 @@ static bool erofs_file_is_compressible(struct erofs_inode *inode)
>
> int erofs_write_file(struct erofs_inode *inode)
> {
> - unsigned int nblocks, i;
> + unsigned int nblocks, i, j, nholes;
> int ret, fd;
> + struct erofs_extent_node *e_node;
>
> if (!inode->i_size) {
> inode->datalayout = EROFS_INODE_FLAT_PLAIN;
> @@ -322,31 +416,43 @@ int erofs_write_file(struct erofs_inode *inode)
> /* fallback to all data uncompressed */
> inode->datalayout = EROFS_INODE_FLAT_INLINE;
> nblocks = inode->i_size / EROFS_BLKSIZ;
> -
> - ret = __allocate_inode_bh_data(inode, nblocks);
> + nholes = erofs_read_extents(inode, &inode->i_extents);
> + if (nholes < 0)
> + return nholes;
> + if (nblocks < 0)
> + return nblocks;
> + ret = __allocate_inode_bh_data(inode, nblocks - nholes);
> if (ret)
> return ret;
>
> fd = open(inode->i_srcpath, O_RDONLY | O_BINARY);
> if (fd < 0)
> return -errno;
> -
> - for (i = 0; i < nblocks; ++i) {
> - char buf[EROFS_BLKSIZ];
> -
> - ret = read(fd, buf, EROFS_BLKSIZ);
> - if (ret != EROFS_BLKSIZ) {
> - if (ret < 0)
> - goto fail;
> - close(fd);
> - return -EAGAIN;
> + i = inode->u.i_blkaddr;
> + inode->extent_meta_isize = sizeof(struct erofs_inline_extent_header);
> + list_for_each_entry(e_node, &inode->i_extents, next) {
> + inode->extent_meta_isize += sizeof(struct erofs_extent);
> + if (e_node->pblk == HOLE_BLK) {
> + lseek(fd, e_node->len * EROFS_BLKSIZ, SEEK_CUR);
> + continue;
> }
> + e_node->pblk = i;
> + i += e_node->len;
> + for (j = 0; j < e_node->len; j++) {
> + char buf[EROFS_BLKSIZ];
> + ret = read(fd, buf, EROFS_BLKSIZ);
> + if (ret != EROFS_BLKSIZ) {
> + if (ret < 0)
> + goto fail;
> + close(fd);
> + return -EAGAIN;
> + }
> + ret = blk_write(buf, e_node->pblk + j, 1);
> + if (ret)
> + goto fail;
>
> - ret = blk_write(buf, inode->u.i_blkaddr + i, 1);
> - if (ret)
> - goto fail;
> + }
> }
> -
> /* read the tail-end data */
> inode->idata_size = inode->i_size % EROFS_BLKSIZ;
> if (inode->idata_size) {
> @@ -479,8 +585,19 @@ static bool erofs_bh_flush_write_inode(struct erofs_buffer_head *bh)
> if (ret)
> return false;
> free(inode->compressmeta);
> + off += inode->extent_isize;
> }
>
> + if (inode->extent_meta_isize) {
> + char *extents = erofs_create_extent_buffer(&inode->i_extents,
> + inode->extent_meta_isize);
> + if (IS_ERR(extents))
> + return false;
> + ret = dev_write(extents, off, inode->extent_meta_isize);
> + free(extents);
> + if (ret)
> + return false;
> + }
> inode->bh = NULL;
> erofs_iput(inode);
> return erofs_bh_flush_generic_end(bh);
> @@ -737,10 +854,11 @@ struct erofs_inode *erofs_new_inode(void)
>
> init_list_head(&inode->i_subdirs);
> init_list_head(&inode->i_xattrs);
> + init_list_head(&inode->i_extents);
>
> inode->idata_size = 0;
> inode->xattr_isize = 0;
> - inode->extent_isize = 0;
> + inode->extent_meta_isize = 0;
>
> inode->bh = inode->bh_inline = inode->bh_data = NULL;
> inode->idata = NULL;
> @@ -961,4 +1079,3 @@ struct erofs_inode *erofs_mkfs_build_tree_from_path(struct erofs_inode *parent,
>
> return erofs_mkfs_build_tree(inode);
> }
> -
> --
> 2.9.3
>
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