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disk/loopback: Support transparent decompression of backing file

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A new option is added to the loopback command, -D or --decompress, which
when specified transparently decompresses the backing file. This allows
compressed images to be used as if they were uncompressed.

Add documentation to support this change.

Suggested-by: Li Gen <ligenlive@gmail.com>
Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Glenn Washburn 2022-08-25 23:08:57 -05:00 committed by Daniel Kiper
parent 641e8391a5
commit 084dfe6d9c
2 changed files with 11 additions and 4 deletions
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5
docs/grub.texi
View File

@ -4938,7 +4938,7 @@ suffix @samp{.pf2} appended. @xref{Theme file format,,Fonts}.
@node loopback
@subsection loopback
@deffn Command loopback [@option{-d}] device file
@deffn Command loopback [@option{-d}] [@option{-D}] device file
Make the device named @var{device} correspond to the contents of the
filesystem image in @var{file}. For example:
@ -4947,6 +4947,9 @@ loopback loop0 /path/to/image
ls (loop0)/
@end example
Specifying the @option{-D} option allows the loopback file to be tranparently
decompressed if there is an appropriate decompressor loaded.
With the @option{-d} option, delete a device previously created using this
command.
@end deffn

10
grub-core/disk/loopback.c
View File

@ -43,6 +43,7 @@ static const struct grub_arg_option options[] =
/* TRANSLATORS: The disk is simply removed from the list of available ones,
not wiped, avoid to scare user. */
{"delete", 'd', 0, N_("Delete the specified loopback drive."), 0, 0},
{"decompress", 'D', 0, N_("Transparently decompress backing file."), 0, 0},
{0, 0, 0, 0, 0, 0}
};
@ -79,6 +80,7 @@ grub_cmd_loopback (grub_extcmd_context_t ctxt, int argc, char **args)
{
struct grub_arg_list *state = ctxt->state;
grub_file_t file;
enum grub_file_type type = GRUB_FILE_TYPE_LOOPBACK;
struct grub_loopback *newdev;
grub_err_t ret;
@ -89,6 +91,9 @@ grub_cmd_loopback (grub_extcmd_context_t ctxt, int argc, char **args)
if (state[0].set)
return delete_loopback (args[0]);
if (!state[1].set)
type |= GRUB_FILE_TYPE_NO_DECOMPRESS;
if (argc < 2)
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
@ -97,8 +102,7 @@ grub_cmd_loopback (grub_extcmd_context_t ctxt, int argc, char **args)
if (grub_strcmp (newdev->devname, args[0]) == 0)
return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name already exists");
file = grub_file_open (args[1], GRUB_FILE_TYPE_LOOPBACK
| GRUB_FILE_TYPE_NO_DECOMPRESS);
file = grub_file_open (args[1], type);
if (! file)
return grub_errno;
@ -226,7 +230,7 @@ static grub_extcmd_t cmd;
GRUB_MOD_INIT(loopback)
{
cmd = grub_register_extcmd ("loopback", grub_cmd_loopback, 0,
N_("[-d] DEVICENAME FILE."),
N_("[-d] [-D] DEVICENAME FILE."),
/* TRANSLATORS: The file itself is not destroyed
or transformed into drive. */
N_("Make a virtual drive from a file."), options);