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author | Yasmin Beatriz <yasmins@linux.vnet.ibm.com> | 2018-02-12 12:25:06 -0200 |
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committer | Marc-André Lureau <marcandre.lureau@redhat.com> | 2018-03-21 14:55:49 +0100 |
commit | 0c33659d09f4a8ab926846295538d6a67e8c2c63 (patch) | |
tree | a58c0c12b9fed4050da7836561c98b35d2f3f831 /roms | |
parent | f1a63fcfcd92c88be8942b5ae71aef9749a4f135 (diff) |
dump.c: allow fd_write_vmcore to return errno on failure
fd_write_vmcore can fail to execute for a lot of reasons that can be
retrieved by errno, but it only returns -1. This makes difficult for
the caller to know what happened and only a generic error message is
propagated back to the user. This is an example using dump-guest-memory:
(qemu) dump-guest-memory /home/yasmin/mnt/test.dump
dump: failed to save memory
All callers of fd_write_vmcore of dump.c does error handling via
error_setg(), so at first it seems feasible to add the Error pointer as
an argument of fd_write_vmcore. This proved to be more complex than it
first looked. fd_write_vmcore is used by write_elf64_notes and
write_elf32_notes as a WriteCoreDumpFunction prototype. WriteCoreDumpFunction
is declared in include/qom/cpu.h and is used all around the code. This
leaves us with few alternatives:
- change the WriteCoreDumpFunction prototype to include an error pointer.
This would require to change all functions that implements this prototype
to also receive an Error pointer;
- change both write_elf64_notes and write_elf32_notes to no use the
WriteCoreDumpFunction. These functions use not only fd_write_vmcore
but also buf_write_note, so this would require to change buf_write_note
to handle an Error pointer. Considerable easier than the alternative
above, but it's still a lot of code just for the benefit of the callers
of fd_write_vmcore.
This patch presents an easier solution that benefits all fd_write_vmcore
callers:
- instead of returning -1 on error, return -errno. All existing callers
already checks for ret < 0 so there is no need to change the caller's
logic too much. This also allows the retrieval of the errno.
- all callers were updated to use error_setg_errno instead of just
errno_setg. Now that fd_write_vmcore can return an errno, let's update
all callers so they can benefit from a more detailed error message.
This is the same dump-guest-memory example with this patch applied:
(qemu) dump-guest-memory /home/yasmin/mnt/test.dump
dump: failed to save memory: No space left on device
(qemu)
This example illustrates an error of fd_write_vmcore when called
from write_data. All other callers will benefit from better
error messages as well.
Reported-by: yilzhang@redhat.com
Cc: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
Signed-off-by: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
Message-Id: <20180212142506.28445-2-danielhb@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Diffstat (limited to 'roms')
0 files changed, 0 insertions, 0 deletions