[PATCH 4/4] erofs: add on-disk compression configurations
Chao Yu
yuchao0 at huawei.com
Sat Mar 27 20:46:44 AEDT 2021
On 2021/3/27 11:49, Gao Xiang wrote:
> From: Gao Xiang <hsiangkao at redhat.com>
>
> Add a bitmap for available compression algorithms and a variable-sized
> on-disk table for compression options in preparation for upcoming big
> pcluster and LZMA algorithm, which follows the end of super block.
>
> To parse the compression options, the bitmap is scanned one by one.
> For each available algorithm, there is data followed by 2-byte `length'
> correspondingly (it's enough for most cases, or entire fs blocks should
> be used.)
>
> With such available algorithm bitmap, kernel itself can also refuse to
> mount such filesystem if any unsupported compression algorithm exists.
>
> Signed-off-by: Gao Xiang <hsiangkao at redhat.com>
> ---
> fs/erofs/decompressor.c | 2 +-
> fs/erofs/erofs_fs.h | 16 +++--
> fs/erofs/internal.h | 5 +-
> fs/erofs/super.c | 145 +++++++++++++++++++++++++++++++++++++++-
> 4 files changed, 161 insertions(+), 7 deletions(-)
>
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index 97538ff24a19..27aa6a99b371 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -41,7 +41,7 @@ int z_erofs_load_lz4_config(struct super_block *sb,
> }
> distance = le16_to_cpu(lz4->max_distance);
> } else {
> - distance = le16_to_cpu(dsb->lz4_max_distance);
> + distance = le16_to_cpu(dsb->u1.lz4_max_distance);
> }
>
> EROFS_SB(sb)->lz4.max_distance_pages = distance ?
> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> index 1322ae63944b..ef3f8a99aa5f 100644
> --- a/fs/erofs/erofs_fs.h
> +++ b/fs/erofs/erofs_fs.h
> @@ -18,15 +18,18 @@
> * be incompatible with this kernel version.
> */
> #define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING 0x00000001
> -#define EROFS_ALL_FEATURE_INCOMPAT EROFS_FEATURE_INCOMPAT_LZ4_0PADDING
> +#define EROFS_FEATURE_INCOMPAT_COMPR_CFGS 0x00000002
> +#define EROFS_ALL_FEATURE_INCOMPAT \
> + (EROFS_FEATURE_INCOMPAT_LZ4_0PADDING | \
> + EROFS_FEATURE_INCOMPAT_COMPR_CFGS)
>
> -/* 128-byte erofs on-disk super block */
> +/* erofs on-disk super block (currently 128 bytes) */
> struct erofs_super_block {
> __le32 magic; /* file system magic number */
> __le32 checksum; /* crc32c(super_block) */
> __le32 feature_compat;
> __u8 blkszbits; /* support block_size == PAGE_SIZE only */
> - __u8 reserved;
> + __u8 sb_extslots; /* superblock size = 128 + sb_extslots * 16 */
>
> __le16 root_nid; /* nid of root directory */
> __le64 inos; /* total valid ino # (== f_files - f_favail) */
> @@ -39,7 +42,11 @@ struct erofs_super_block {
> __u8 uuid[16]; /* 128-bit uuid for volume */
> __u8 volume_name[16]; /* volume name */
> __le32 feature_incompat;
> - __le16 lz4_max_distance;
> + union {
> + /* bitmap for available compression algorithms */
> + __le16 available_compr_algs;
> + __le16 lz4_max_distance;
> + } __packed u1;
> __u8 reserved2[42];
> };
>
> @@ -195,6 +202,7 @@ enum {
> Z_EROFS_COMPRESSION_LZ4 = 0,
> Z_EROFS_COMPRESSION_MAX
> };
> +#define Z_EROFS_ALL_COMPR_ALGS (1 << (Z_EROFS_COMPRESSION_MAX - 1))
>
> /* 14 bytes (+ length field = 16 bytes) */
> struct z_erofs_lz4_cfgs {
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 46b977f348eb..f3fa895d809f 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -75,6 +75,7 @@ struct erofs_sb_info {
> struct xarray managed_pslots;
>
> unsigned int shrinker_run_no;
> + u16 available_compr_algs;
>
> /* pseudo inode to manage cached pages */
> struct inode *managed_cache;
> @@ -90,6 +91,7 @@ struct erofs_sb_info {
> /* inode slot unit size in bit shift */
> unsigned char islotbits;
>
> + u32 sb_size; /* total superblock size */
> u32 build_time_nsec;
> u64 build_time;
>
> @@ -233,6 +235,7 @@ static inline bool erofs_sb_has_##name(struct erofs_sb_info *sbi) \
> }
>
> EROFS_FEATURE_FUNCS(lz4_0padding, incompat, INCOMPAT_LZ4_0PADDING)
> +EROFS_FEATURE_FUNCS(compr_cfgs, incompat, INCOMPAT_COMPR_CFGS)
> EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
>
> /* atomic flag definitions */
> @@ -454,7 +457,7 @@ static inline int z_erofs_load_lz4_config(struct super_block *sb,
> struct erofs_super_block *dsb,
> struct z_erofs_lz4_cfgs *lz4, int len)
> {
> - if (lz4 || dsb->lz4_max_distance) {
> + if (lz4 || dsb->u1.lz4_max_distance) {
> erofs_err(sb, "lz4 algorithm isn't enabled");
> return -EINVAL;
> }
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 1ca8da3f2125..c5e3039f51bf 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -122,6 +122,138 @@ static bool check_layout_compatibility(struct super_block *sb,
> return true;
> }
>
> +#ifdef CONFIG_EROFS_FS_ZIP
> +/* read variable-sized metadata, offset will be aligned by 4-byte */
> +static void *erofs_read_metadata(struct super_block *sb, struct page **pagep,
> + erofs_off_t *offset, int *lengthp)
> +{
> + struct page *page = *pagep;
> + u8 *buffer, *ptr;
> + int len, i, cnt;
> + erofs_blk_t blk;
> +
> + *offset = round_up(*offset, 4);
> + blk = erofs_blknr(*offset);
> +
> + if (!page || page->index != blk) {
> + if (page) {
> + unlock_page(page);
> + put_page(page);
> + }
> + page = erofs_get_meta_page(sb, blk);
> + if (IS_ERR(page))
> + goto err_nullpage;
> + }
> +
> + ptr = kmap(page);
> + len = le16_to_cpu(*(__le16 *)&ptr[erofs_blkoff(*offset)]);
> + if (!len)
> + len = U16_MAX + 1;
> + buffer = kmalloc(len, GFP_KERNEL);
> + if (!buffer) {
> + buffer = ERR_PTR(-ENOMEM);
Caller expects valid page w/o kmapped or a NULL page, right? it needs
to call kunmap() here? or out label can be relocated above kunmap()?
Thanks,
> + goto out;
> + }
> + *offset += sizeof(__le16);
> + *lengthp = len;
> +
> + for (i = 0; i < len; i += cnt) {
> + cnt = min(EROFS_BLKSIZ - (int)erofs_blkoff(*offset), len - i);
> + blk = erofs_blknr(*offset);
> +
> + if (!page || page->index != blk) {
> + if (page) {
> + kunmap(page);
> + unlock_page(page);
> + put_page(page);
> + }
> + page = erofs_get_meta_page(sb, blk);
> + if (IS_ERR(page)) {
> + kfree(buffer);
> + goto err_nullpage;
> + }
> + ptr = kmap(page);
> + }
> + memcpy(buffer + i, ptr + erofs_blkoff(*offset), cnt);
> + *offset += cnt;
> + }
> + kunmap(page);
> +out:
> + *pagep = page;
> + return buffer;
> +err_nullpage:
> + *pagep = NULL;
> + return page;
> +}
> +
> +static int erofs_load_compr_cfgs(struct super_block *sb,
> + struct erofs_super_block *dsb)
> +{
> + struct erofs_sb_info *sbi;
> + struct page *page;
> + unsigned int algs, alg;
> + erofs_off_t offset;
> + int size, ret;
> +
> + sbi = EROFS_SB(sb);
> + sbi->available_compr_algs = le16_to_cpu(dsb->u1.available_compr_algs);
> +
> + if (sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS) {
> + erofs_err(sb,
> +"try to load compressed image with unsupported algorithms %x",
> + sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS);
> + return -EINVAL;
> + }
> +
> + offset = EROFS_SUPER_OFFSET + sbi->sb_size;
> + page = NULL;
> + alg = 0;
> + ret = 0;
> +
> + for (algs = sbi->available_compr_algs; algs; algs >>= 1, ++alg) {
> + void *data;
> +
> + if (!(algs & 1))
> + continue;
> +
> + data = erofs_read_metadata(sb, &page, &offset, &size);
> + if (IS_ERR(data)) {
> + ret = PTR_ERR(data);
> + goto err;
> + }
> +
> + switch (alg) {
> + case Z_EROFS_COMPRESSION_LZ4:
> + ret = z_erofs_load_lz4_config(sb, dsb, data, size);
> + break;
> + default:
> + DBG_BUGON(1);
> + ret = -EFAULT;
> + }
> + kfree(data);
> + if (ret)
> + goto err;
> + }
> +err:
> + if (page) {
> + unlock_page(page);
> + put_page(page);
> + }
> + return ret;
> +}
> +#else
> +static int erofs_load_compr_cfgs(struct super_block *sb,
> + struct erofs_super_block *dsb)
> +{
> + if (dsb->u1.available_compr_algs) {
> + erofs_err(sb,
> +"try to load compressed image when compression is disabled");
> + return -EINVAL;
> + }
> + return 0;
> +}
> +#endif
> +
> static int erofs_read_superblock(struct super_block *sb)
> {
> struct erofs_sb_info *sbi;
> @@ -166,6 +298,13 @@ static int erofs_read_superblock(struct super_block *sb)
> if (!check_layout_compatibility(sb, dsb))
> goto out;
>
> + sbi->sb_size = 128 + dsb->sb_extslots * 16;
> + if (sbi->sb_size > EROFS_BLKSIZ) {
> + erofs_err(sb, "invalid sb_extslots %u (more than a fs block)",
> + sbi->sb_size);
> + goto out;
> + }
> +
> sbi->blocks = le32_to_cpu(dsb->blocks);
> sbi->meta_blkaddr = le32_to_cpu(dsb->meta_blkaddr);
> #ifdef CONFIG_EROFS_FS_XATTR
> @@ -189,7 +328,11 @@ static int erofs_read_superblock(struct super_block *sb)
> }
>
> /* parse on-disk compression configurations */
> - ret = z_erofs_load_lz4_config(sb, dsb, NULL, 0);
> + if (erofs_sb_has_compr_cfgs(sbi))
> + ret = erofs_load_compr_cfgs(sb, dsb);
> + else
> + ret = z_erofs_load_lz4_config(sb, dsb, NULL, 0);
> +
> out:
> kunmap(page);
> put_page(page);
>
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