On Sat, Feb 18, 2017, 10:17 Andrei Borzenkov <arvidj...@gmail.com> wrote:
> 1. Do not assume block list and fragment are mutually exclusive. Squash
> can pack file tail as fragment (unless -no-fragments is specified); so
> check read offset and read either from block list or from fragments as
> appropriate.
>
> 2. Support sparse files with zero blocks.
>
> 3. Fix fragment read - frag.offset is absolute fragment position,
> not offset relative to ino.chunk.
>
Go ahead.
>
> Reported and tested by Carlo Caione <ca...@endlessm.com>
>
> ---
>
> @Vladimir: we need regression tests for both of these cases. We could real
> small
> files only by accident - block list was zero, so it appeared to work.
>
How do you create those files reliably? Feel free to add any files to
grub-fs-tester. Feel free to commit without tests, we can add tests later.
>
> @Carlo, please test. I'm surprised it worked for you even without
> fragments as
> your file is sparse and grub immediately choked on the first zero block.
>
> grub-core/fs/squash4.c | 55
> +++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 36 insertions(+), 19 deletions(-)
>
> diff --git a/grub-core/fs/squash4.c b/grub-core/fs/squash4.c
> index b97b344..deee71a 100644
> --- a/grub-core/fs/squash4.c
> +++ b/grub-core/fs/squash4.c
> @@ -823,7 +823,12 @@ direct_read (struct grub_squash_data *data,
> curread = data->blksz - boff;
> if (curread > len)
> curread = len;
> - if (!(ino->block_sizes[i]
> + if (!ino->block_sizes[i])
> + {
> + /* Sparse block */
> + grub_memset (buf, '\0', curread);
> + }
> + else if (!(ino->block_sizes[i]
> & grub_cpu_to_le32_compile_time (SQUASH_BLOCK_UNCOMPRESSED)))
> {
> char *block;
> @@ -873,36 +878,57 @@ direct_read (struct grub_squash_data *data,
>
>
> static grub_ssize_t
> -grub_squash_read_data (struct grub_squash_data *data,
> - struct grub_squash_cache_inode *ino,
> - grub_off_t off, char *buf, grub_size_t len)
> +grub_squash_read (grub_file_t file, char *buf, grub_size_t len)
> {
> + struct grub_squash_data *data = file->data;
> + struct grub_squash_cache_inode *ino = &data->ino;
> + grub_off_t off = file->offset;
> grub_err_t err;
> grub_uint64_t a = 0, b;
> grub_uint32_t fragment = 0;
> int compressed = 0;
> struct grub_squash_frag_desc frag;
> + grub_off_t blk_len;
> + grub_uint64_t mask = grub_le_to_cpu32 (data->sb.block_size) - 1;
> + grub_size_t orig_len = len;
>
> switch (ino->ino.type)
> {
> case grub_cpu_to_le16_compile_time (SQUASH_TYPE_LONG_REGULAR):
> - a = grub_le_to_cpu64 (ino->ino.long_file.chunk);
> fragment = grub_le_to_cpu32 (ino->ino.long_file.fragment);
> break;
> case grub_cpu_to_le16_compile_time (SQUASH_TYPE_REGULAR):
> - a = grub_le_to_cpu32 (ino->ino.file.chunk);
> fragment = grub_le_to_cpu32 (ino->ino.file.fragment);
> break;
> }
>
> - if (fragment == 0xffffffff)
> - return direct_read (data, ino, off, buf, len);
> + /* Squash may pack file tail as fragment. So read initial part directly
> and
> + get tail from fragments */
> + blk_len = fragment == 0xffffffff ? file->size : file->size & ~mask;
> + if (off < blk_len)
> + {
> + grub_size_t read_len = blk_len - off;
> + grub_ssize_t res;
> +
> + if (read_len > len)
> + read_len = len;
> + res = direct_read (data, ino, off, buf, read_len);
> + if ((grub_size_t) res != read_len)
> + return -1; /* FIXME: is short read possible here? */
> + len -= read_len;
> + if (!len)
> + return read_len;
> + buf += read_len;
> + off = 0;
> + }
> + else
> + off -= blk_len;
>
> err = read_chunk (data, &frag, sizeof (frag),
> data->fragments, sizeof (frag) * fragment);
> if (err)
> return -1;
> - a += grub_le_to_cpu64 (frag.offset);
> + a = grub_le_to_cpu64 (frag.offset);
> compressed = !(frag.size & grub_cpu_to_le32_compile_time
> (SQUASH_BLOCK_UNCOMPRESSED));
> if (ino->ino.type == grub_cpu_to_le16_compile_time
> (SQUASH_TYPE_LONG_REGULAR))
> b = grub_le_to_cpu32 (ino->ino.long_file.offset) + off;
> @@ -943,16 +969,7 @@ grub_squash_read_data (struct grub_squash_data *data,
> if (err)
> return -1;
> }
> - return len;
> -}
> -
> -static grub_ssize_t
> -grub_squash_read (grub_file_t file, char *buf, grub_size_t len)
> -{
> - struct grub_squash_data *data = file->data;
> -
> - return grub_squash_read_data (data, &data->ino,
> - file->offset, buf, len);
> + return orig_len;
> }
>
> static grub_err_t
> --
> tg: (2fb8cd2..) u/squash-tail-fragment (depends on: master)
>
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>
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