* [Qemu-devel] [PATCH v3 0/1] dump.c: allow fd_write_vmcore to return errno on failure
@ 2018-02-12 14:25 Daniel Henrique Barboza
2018-02-12 14:25 ` [Qemu-devel] [PATCH v3 1/1] " Daniel Henrique Barboza
2018-03-21 13:29 ` [Qemu-devel] [PATCH v3 0/1] " Daniel Henrique Barboza
0 siblings, 2 replies; 11+ messages in thread
From: Daniel Henrique Barboza @ 2018-02-12 14:25 UTC (permalink / raw)
To: qemu-devel; +Cc: marcandre.lureau, eblake, Daniel Henrique Barboza
v3:
- added set_errg_errno() to all callers of fd_write_vmcore
- changed patch subject to reflect what it is addressing now
- link to previous version:
http://lists.gnu.org/archive/html/qemu-devel/2018-02/msg02787.html
Yasmin Beatriz (1):
dump.c: allow fd_write_vmcore to return errno on failure
dump.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
--
2.14.3
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Qemu-devel] [PATCH v3 1/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 14:25 [Qemu-devel] [PATCH v3 0/1] dump.c: allow fd_write_vmcore to return errno on failure Daniel Henrique Barboza
@ 2018-02-12 14:25 ` Daniel Henrique Barboza
2018-02-12 14:31 ` Marc-Andre Lureau
` (2 more replies)
2018-03-21 13:29 ` [Qemu-devel] [PATCH v3 0/1] " Daniel Henrique Barboza
1 sibling, 3 replies; 11+ messages in thread
From: Daniel Henrique Barboza @ 2018-02-12 14:25 UTC (permalink / raw)
To: qemu-devel
Cc: marcandre.lureau, eblake, Yasmin Beatriz, Jose Ricardo Ziviani,
Daniel Henrique Barboza
From: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
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>
---
dump.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/dump.c b/dump.c
index 7b13baa413..171ff8a3b8 100644
--- a/dump.c
+++ b/dump.c
@@ -107,7 +107,7 @@ static int fd_write_vmcore(const void *buf, size_t size, void *opaque)
written_size = qemu_write_full(s->fd, buf, size);
if (written_size != size) {
- return -1;
+ return -errno;
}
return 0;
@@ -140,7 +140,7 @@ static void write_elf64_header(DumpState *s, Error **errp)
ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
if (ret < 0) {
- error_setg(errp, "dump: failed to write elf header");
+ error_setg_errno(errp, -ret, "dump: failed to write elf header");
}
}
@@ -171,7 +171,7 @@ static void write_elf32_header(DumpState *s, Error **errp)
ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
if (ret < 0) {
- error_setg(errp, "dump: failed to write elf header");
+ error_setg_errno(errp, -ret, "dump: failed to write elf header");
}
}
@@ -194,7 +194,8 @@ static void write_elf64_load(DumpState *s, MemoryMapping *memory_mapping,
ret = fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s);
if (ret < 0) {
- error_setg(errp, "dump: failed to write program header table");
+ error_setg_errno(errp, -ret,
+ "dump: failed to write program header table");
}
}
@@ -217,7 +218,8 @@ static void write_elf32_load(DumpState *s, MemoryMapping *memory_mapping,
ret = fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s);
if (ret < 0) {
- error_setg(errp, "dump: failed to write program header table");
+ error_setg_errno(errp, -ret,
+ "dump: failed to write program header table");
}
}
@@ -237,7 +239,8 @@ static void write_elf64_note(DumpState *s, Error **errp)
ret = fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s);
if (ret < 0) {
- error_setg(errp, "dump: failed to write program header table");
+ error_setg_errno(errp, -ret,
+ "dump: failed to write program header table");
}
}
@@ -302,7 +305,8 @@ static void write_elf32_note(DumpState *s, Error **errp)
ret = fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s);
if (ret < 0) {
- error_setg(errp, "dump: failed to write program header table");
+ error_setg_errno(errp, -ret,
+ "dump: failed to write program header table");
}
}
@@ -355,7 +359,8 @@ static void write_elf_section(DumpState *s, int type, Error **errp)
ret = fd_write_vmcore(&shdr, shdr_size, s);
if (ret < 0) {
- error_setg(errp, "dump: failed to write section header table");
+ error_setg_errno(errp, -ret,
+ "dump: failed to write section header table");
}
}
@@ -365,7 +370,7 @@ static void write_data(DumpState *s, void *buf, int length, Error **errp)
ret = fd_write_vmcore(buf, length, s);
if (ret < 0) {
- error_setg(errp, "dump: failed to save memory");
+ error_setg_errno(errp, -ret, "dump: failed to save memory");
} else {
s->written_size += length;
}
--
2.14.3
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 1/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 14:25 ` [Qemu-devel] [PATCH v3 1/1] " Daniel Henrique Barboza
@ 2018-02-12 14:31 ` Marc-Andre Lureau
2018-02-12 14:46 ` Murilo Opsfelder Araujo
2018-02-12 17:47 ` Eric Blake
2 siblings, 0 replies; 11+ messages in thread
From: Marc-Andre Lureau @ 2018-02-12 14:31 UTC (permalink / raw)
To: Daniel Henrique Barboza
Cc: qemu-devel, marcandre, Blake, Eric, Yasmin Beatriz, Jose Ricardo Ziviani
Hi
On Mon, Feb 12, 2018 at 3:25 PM, Daniel Henrique Barboza
<danielhb@linux.vnet.ibm.com> wrote:
> From: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
>
> 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>
lgtm,
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
> dump.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/dump.c b/dump.c
> index 7b13baa413..171ff8a3b8 100644
> --- a/dump.c
> +++ b/dump.c
> @@ -107,7 +107,7 @@ static int fd_write_vmcore(const void *buf, size_t size, void *opaque)
>
> written_size = qemu_write_full(s->fd, buf, size);
> if (written_size != size) {
> - return -1;
> + return -errno;
> }
>
> return 0;
> @@ -140,7 +140,7 @@ static void write_elf64_header(DumpState *s, Error **errp)
>
> ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write elf header");
> + error_setg_errno(errp, -ret, "dump: failed to write elf header");
> }
> }
>
> @@ -171,7 +171,7 @@ static void write_elf32_header(DumpState *s, Error **errp)
>
> ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write elf header");
> + error_setg_errno(errp, -ret, "dump: failed to write elf header");
> }
> }
>
> @@ -194,7 +194,8 @@ static void write_elf64_load(DumpState *s, MemoryMapping *memory_mapping,
>
> ret = fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write program header table");
> + error_setg_errno(errp, -ret,
> + "dump: failed to write program header table");
> }
> }
>
> @@ -217,7 +218,8 @@ static void write_elf32_load(DumpState *s, MemoryMapping *memory_mapping,
>
> ret = fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write program header table");
> + error_setg_errno(errp, -ret,
> + "dump: failed to write program header table");
> }
> }
>
> @@ -237,7 +239,8 @@ static void write_elf64_note(DumpState *s, Error **errp)
>
> ret = fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write program header table");
> + error_setg_errno(errp, -ret,
> + "dump: failed to write program header table");
> }
> }
>
> @@ -302,7 +305,8 @@ static void write_elf32_note(DumpState *s, Error **errp)
>
> ret = fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write program header table");
> + error_setg_errno(errp, -ret,
> + "dump: failed to write program header table");
> }
> }
>
> @@ -355,7 +359,8 @@ static void write_elf_section(DumpState *s, int type, Error **errp)
>
> ret = fd_write_vmcore(&shdr, shdr_size, s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write section header table");
> + error_setg_errno(errp, -ret,
> + "dump: failed to write section header table");
> }
> }
>
> @@ -365,7 +370,7 @@ static void write_data(DumpState *s, void *buf, int length, Error **errp)
>
> ret = fd_write_vmcore(buf, length, s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to save memory");
> + error_setg_errno(errp, -ret, "dump: failed to save memory");
> } else {
> s->written_size += length;
> }
> --
> 2.14.3
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 1/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 14:25 ` [Qemu-devel] [PATCH v3 1/1] " Daniel Henrique Barboza
2018-02-12 14:31 ` Marc-Andre Lureau
@ 2018-02-12 14:46 ` Murilo Opsfelder Araujo
2018-02-12 15:49 ` Daniel Henrique Barboza
2018-02-12 17:31 ` Eric Blake
2018-02-12 17:47 ` Eric Blake
2 siblings, 2 replies; 11+ messages in thread
From: Murilo Opsfelder Araujo @ 2018-02-12 14:46 UTC (permalink / raw)
To: Daniel Henrique Barboza, qemu-devel
Cc: marcandre.lureau, Yasmin Beatriz, Jose Ricardo Ziviani
On 02/12/2018 12:25 PM, Daniel Henrique Barboza wrote:
> From: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
>
> 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>
> ---
> dump.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/dump.c b/dump.c
> index 7b13baa413..171ff8a3b8 100644
> --- a/dump.c
> +++ b/dump.c
> @@ -107,7 +107,7 @@ static int fd_write_vmcore(const void *buf, size_t size, void *opaque)
>
> written_size = qemu_write_full(s->fd, buf, size);
> if (written_size != size) {
> - return -1;
> + return -errno;
> }
>
> return 0;
> @@ -140,7 +140,7 @@ static void write_elf64_header(DumpState *s, Error **errp)
>
> ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
> if (ret < 0) {
> - error_setg(errp, "dump: failed to write elf header");
> + error_setg_errno(errp, -ret, "dump: failed to write elf header");
Do we need -ret passed to error_setg_errno()? fd_write_vmcore() returns
negative errno in case of error.
Cheers
Murilo
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 1/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 14:46 ` Murilo Opsfelder Araujo
@ 2018-02-12 15:49 ` Daniel Henrique Barboza
2018-02-12 17:31 ` Eric Blake
1 sibling, 0 replies; 11+ messages in thread
From: Daniel Henrique Barboza @ 2018-02-12 15:49 UTC (permalink / raw)
To: Murilo Opsfelder Araujo, qemu-devel
Cc: marcandre.lureau, Yasmin Beatriz, Jose Ricardo Ziviani
On 02/12/2018 12:46 PM, Murilo Opsfelder Araujo wrote:
> On 02/12/2018 12:25 PM, Daniel Henrique Barboza wrote:
>> From: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
>>
>> 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>
>> ---
>> dump.c | 23 ++++++++++++++---------
>> 1 file changed, 14 insertions(+), 9 deletions(-)
>>
>> diff --git a/dump.c b/dump.c
>> index 7b13baa413..171ff8a3b8 100644
>> --- a/dump.c
>> +++ b/dump.c
>> @@ -107,7 +107,7 @@ static int fd_write_vmcore(const void *buf, size_t size, void *opaque)
>>
>> written_size = qemu_write_full(s->fd, buf, size);
>> if (written_size != size) {
>> - return -1;
>> + return -errno;
>> }
>>
>> return 0;
>> @@ -140,7 +140,7 @@ static void write_elf64_header(DumpState *s, Error **errp)
>>
>> ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
>> if (ret < 0) {
>> - error_setg(errp, "dump: failed to write elf header");
>> + error_setg_errno(errp, -ret, "dump: failed to write elf header");
> Do we need -ret passed to error_setg_errno()? fd_write_vmcore() returns
> negative errno in case of error.
I am passing -ret here to provide a positive errno value to
error_setg_errno. I
am not sure if os_error can be negative and didn't want to risk
strerror() breaking.
Daniel
>
> Cheers
> Murilo
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 1/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 14:46 ` Murilo Opsfelder Araujo
2018-02-12 15:49 ` Daniel Henrique Barboza
@ 2018-02-12 17:31 ` Eric Blake
2018-02-12 19:19 ` Murilo Opsfelder Araujo
1 sibling, 1 reply; 11+ messages in thread
From: Eric Blake @ 2018-02-12 17:31 UTC (permalink / raw)
To: Murilo Opsfelder Araujo, Daniel Henrique Barboza, qemu-devel
Cc: marcandre.lureau, Jose Ricardo Ziviani, Yasmin Beatriz
On 02/12/2018 08:46 AM, Murilo Opsfelder Araujo wrote:
> On 02/12/2018 12:25 PM, Daniel Henrique Barboza wrote:
>> From: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
>>
>> 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:
>>
>> +++ b/dump.c
>> @@ -107,7 +107,7 @@ static int fd_write_vmcore(const void *buf, size_t size, void *opaque)
>>
>> written_size = qemu_write_full(s->fd, buf, size);
>> if (written_size != size) {
>> - return -1;
>> + return -errno;
>> }
>>
>> return 0;
>> @@ -140,7 +140,7 @@ static void write_elf64_header(DumpState *s, Error **errp)
>>
>> ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
>> if (ret < 0) {
>> - error_setg(errp, "dump: failed to write elf header");
>> + error_setg_errno(errp, -ret, "dump: failed to write elf header");
>
> Do we need -ret passed to error_setg_errno()? fd_write_vmcore() returns
> negative errno in case of error.
Yes, this usage is correct. error_setg_errno() takes a positive errno
value (using strerror, which only decodes positive values into useful
strings); but we typically return negative errno values (as was
correctly done in fd_write_vmcore), so the extra layer of negation here
is needed.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 1/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 14:25 ` [Qemu-devel] [PATCH v3 1/1] " Daniel Henrique Barboza
2018-02-12 14:31 ` Marc-Andre Lureau
2018-02-12 14:46 ` Murilo Opsfelder Araujo
@ 2018-02-12 17:47 ` Eric Blake
2 siblings, 0 replies; 11+ messages in thread
From: Eric Blake @ 2018-02-12 17:47 UTC (permalink / raw)
To: Daniel Henrique Barboza, qemu-devel
Cc: marcandre.lureau, Yasmin Beatriz, Jose Ricardo Ziviani
On 02/12/2018 08:25 AM, Daniel Henrique Barboza wrote:
> From: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
>
> 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
>
...
> 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>
> ---
> dump.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 1/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 17:31 ` Eric Blake
@ 2018-02-12 19:19 ` Murilo Opsfelder Araujo
0 siblings, 0 replies; 11+ messages in thread
From: Murilo Opsfelder Araujo @ 2018-02-12 19:19 UTC (permalink / raw)
To: Eric Blake, Daniel Henrique Barboza, qemu-devel
Cc: marcandre.lureau, Jose Ricardo Ziviani, Yasmin Beatriz
On 02/12/2018 03:31 PM, Eric Blake wrote:
> On 02/12/2018 08:46 AM, Murilo Opsfelder Araujo wrote:
>> On 02/12/2018 12:25 PM, Daniel Henrique Barboza wrote:
>>> From: Yasmin Beatriz <yasmins@linux.vnet.ibm.com>
>>>
>>> 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:
>>>
>
>>> +++ b/dump.c
>>> @@ -107,7 +107,7 @@ static int fd_write_vmcore(const void *buf,
>>> size_t size, void *opaque)
>>>
>>> written_size = qemu_write_full(s->fd, buf, size);
>>> if (written_size != size) {
>>> - return -1;
>>> + return -errno;
>>> }
>>>
>>> return 0;
>>> @@ -140,7 +140,7 @@ static void write_elf64_header(DumpState *s,
>>> Error **errp)
>>>
>>> ret = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
>>> if (ret < 0) {
>>> - error_setg(errp, "dump: failed to write elf header");
>>> + error_setg_errno(errp, -ret, "dump: failed to write elf
>>> header");
>>
>> Do we need -ret passed to error_setg_errno()? fd_write_vmcore() returns
>> negative errno in case of error.
>
> Yes, this usage is correct. error_setg_errno() takes a positive errno
> value (using strerror, which only decodes positive values into useful
> strings); but we typically return negative errno values (as was
> correctly done in fd_write_vmcore), so the extra layer of negation here
> is needed.
>
For some reason I assumed "non-zero" in the error_setg_errno()
description as negative.
Thanks Daniel and Eric.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 0/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-02-12 14:25 [Qemu-devel] [PATCH v3 0/1] dump.c: allow fd_write_vmcore to return errno on failure Daniel Henrique Barboza
2018-02-12 14:25 ` [Qemu-devel] [PATCH v3 1/1] " Daniel Henrique Barboza
@ 2018-03-21 13:29 ` Daniel Henrique Barboza
2018-03-21 13:56 ` [Qemu-devel] [PATCH v3 for-2.12? " Eric Blake
1 sibling, 1 reply; 11+ messages in thread
From: Daniel Henrique Barboza @ 2018-03-21 13:29 UTC (permalink / raw)
To: qemu-devel; +Cc: marcandre.lureau, Laurent Vivier, Eric Blake
Ping
On 02/12/2018 12:25 PM, Daniel Henrique Barboza wrote:
> v3:
> - added set_errg_errno() to all callers of fd_write_vmcore
> - changed patch subject to reflect what it is addressing now
> - link to previous version:
> http://lists.gnu.org/archive/html/qemu-devel/2018-02/msg02787.html
>
>
> Yasmin Beatriz (1):
> dump.c: allow fd_write_vmcore to return errno on failure
>
> dump.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 for-2.12? 0/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-03-21 13:29 ` [Qemu-devel] [PATCH v3 0/1] " Daniel Henrique Barboza
@ 2018-03-21 13:56 ` Eric Blake
2018-03-21 14:20 ` Marc-André Lureau
0 siblings, 1 reply; 11+ messages in thread
From: Eric Blake @ 2018-03-21 13:56 UTC (permalink / raw)
To: Daniel Henrique Barboza, qemu-devel
Cc: marcandre.lureau, Laurent Vivier, Paolo Bonzini
On 03/21/2018 08:29 AM, Daniel Henrique Barboza wrote:
> Ping
>
> On 02/12/2018 12:25 PM, Daniel Henrique Barboza wrote:
>> v3:
>> - added set_errg_errno() to all callers of fd_write_vmcore
>> - changed patch subject to reflect what it is addressing now
>> - link to previous version:
>> http://lists.gnu.org/archive/html/qemu-devel/2018-02/msg02787.html
>>
>>
>> Yasmin Beatriz (1):
>> dump.c: allow fd_write_vmcore to return errno on failure
>>
>> dump.c | 23 ++++++++++++++---------
>> 1 file changed, 14 insertions(+), 9 deletions(-)
>>
This seems like an appropriate bug-fix patch for inclusion in 2.12.
Marc-André, are you planning a pull request, or should we bundle this
through another miscellaneous tree?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [Qemu-devel] [PATCH v3 for-2.12? 0/1] dump.c: allow fd_write_vmcore to return errno on failure
2018-03-21 13:56 ` [Qemu-devel] [PATCH v3 for-2.12? " Eric Blake
@ 2018-03-21 14:20 ` Marc-André Lureau
0 siblings, 0 replies; 11+ messages in thread
From: Marc-André Lureau @ 2018-03-21 14:20 UTC (permalink / raw)
To: Eric Blake
Cc: Daniel Henrique Barboza, qemu-devel, Laurent Vivier, Paolo Bonzini
Hi
On Wed, Mar 21, 2018 at 2:56 PM, Eric Blake <eblake@redhat.com> wrote:
> On 03/21/2018 08:29 AM, Daniel Henrique Barboza wrote:
>>
>> Ping
>>
>> On 02/12/2018 12:25 PM, Daniel Henrique Barboza wrote:
>>>
>>> v3:
>>> - added set_errg_errno() to all callers of fd_write_vmcore
>>> - changed patch subject to reflect what it is addressing now
>>> - link to previous version:
>>> http://lists.gnu.org/archive/html/qemu-devel/2018-02/msg02787.html
>>>
>>>
>>> Yasmin Beatriz (1):
>>> dump.c: allow fd_write_vmcore to return errno on failure
>>>
>>> dump.c | 23 ++++++++++++++---------
>>> 1 file changed, 14 insertions(+), 9 deletions(-)
>>>
>
> This seems like an appropriate bug-fix patch for inclusion in 2.12.
> Marc-André, are you planning a pull request, or should we bundle this
> through another miscellaneous tree?
Ok, I'll prepare a pull request.
Thanks
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2018-03-21 14:20 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-02-12 14:25 [Qemu-devel] [PATCH v3 0/1] dump.c: allow fd_write_vmcore to return errno on failure Daniel Henrique Barboza
2018-02-12 14:25 ` [Qemu-devel] [PATCH v3 1/1] " Daniel Henrique Barboza
2018-02-12 14:31 ` Marc-Andre Lureau
2018-02-12 14:46 ` Murilo Opsfelder Araujo
2018-02-12 15:49 ` Daniel Henrique Barboza
2018-02-12 17:31 ` Eric Blake
2018-02-12 19:19 ` Murilo Opsfelder Araujo
2018-02-12 17:47 ` Eric Blake
2018-03-21 13:29 ` [Qemu-devel] [PATCH v3 0/1] " Daniel Henrique Barboza
2018-03-21 13:56 ` [Qemu-devel] [PATCH v3 for-2.12? " Eric Blake
2018-03-21 14:20 ` Marc-André Lureau
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