| Message ID | 20201202203242.1187898-1-nickrterrell@gmail.com |
|---|---|
| Headers | show |
| Series | Update to zstd-1.4.6 | expand |
On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote: > From: Nick Terrell <terrelln@fb.com> > > This patch: > - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h` > - Adds a new API in `include/linux/zstd.h` that is functionally > equivalent to the in-use subset of the current API. Functions are > renamed to avoid symbol collisions with zstd, to make it clear it is > not the upstream zstd API, and to follow the kernel style guide. > - Updates all callers to use the new API. > > There are no functional changes in this patch. Since there are no > functional change, I felt it was okay to update all the callers in a > single patch, since once the API is approved, the callers are > mechanically changed. [...] > --- a/lib/decompress_unzstd.c > +++ b/lib/decompress_unzstd.c [...] > static int INIT handle_zstd_error(size_t ret, void (*error)(char *x)) > { > - const int err = ZSTD_getErrorCode(ret); > - > - if (!ZSTD_isError(ret)) > + if (!zstd_is_error(ret)) > return 0; > > - switch (err) { > - case ZSTD_error_memory_allocation: > - error("ZSTD decompressor ran out of memory"); > - break; > - case ZSTD_error_prefix_unknown: > - error("Input is not in the ZSTD format (wrong magic bytes)"); > - break; > - case ZSTD_error_dstSize_tooSmall: > - case ZSTD_error_corruption_detected: > - case ZSTD_error_checksum_wrong: > - error("ZSTD-compressed data is corrupt"); > - break; > - default: > - error("ZSTD-compressed data is probably corrupt"); > - break; > - } > + error("ZSTD decompression failed"); > return -1; > } This looses diagnostics specificity - is this intended? At least the out-of-memory condition seems useful to distinguish. > +size_t zstd_compress_stream(zstd_cstream *cstream, > + struct zstd_out_buffer *output, struct zstd_in_buffer *input) > +{ > + ZSTD_outBuffer o; > + ZSTD_inBuffer i; > + size_t ret; > + > + memcpy(&o, output, sizeof(o)); > + memcpy(&i, input, sizeof(i)); > + ret = ZSTD_compressStream(cstream, &o, &i); > + memcpy(output, &o, sizeof(o)); > + memcpy(input, &i, sizeof(i)); > + return ret; > +} Is all this copying necessary? How is it different from type-punning by direct pointer cast? Best Regards Michał Mirosław
> On Dec 2, 2020, at 5:16 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: > > On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote: >> From: Nick Terrell <terrelln@fb.com> >> >> This patch: >> - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h` >> - Adds a new API in `include/linux/zstd.h` that is functionally >> equivalent to the in-use subset of the current API. Functions are >> renamed to avoid symbol collisions with zstd, to make it clear it is >> not the upstream zstd API, and to follow the kernel style guide. >> - Updates all callers to use the new API. >> >> There are no functional changes in this patch. Since there are no >> functional change, I felt it was okay to update all the callers in a >> single patch, since once the API is approved, the callers are >> mechanically changed. > [...] >> --- a/lib/decompress_unzstd.c >> +++ b/lib/decompress_unzstd.c > [...] >> static int INIT handle_zstd_error(size_t ret, void (*error)(char *x)) >> { >> - const int err = ZSTD_getErrorCode(ret); >> - >> - if (!ZSTD_isError(ret)) >> + if (!zstd_is_error(ret)) >> return 0; >> >> - switch (err) { >> - case ZSTD_error_memory_allocation: >> - error("ZSTD decompressor ran out of memory"); >> - break; >> - case ZSTD_error_prefix_unknown: >> - error("Input is not in the ZSTD format (wrong magic bytes)"); >> - break; >> - case ZSTD_error_dstSize_tooSmall: >> - case ZSTD_error_corruption_detected: >> - case ZSTD_error_checksum_wrong: >> - error("ZSTD-compressed data is corrupt"); >> - break; >> - default: >> - error("ZSTD-compressed data is probably corrupt"); >> - break; >> - } >> + error("ZSTD decompression failed"); >> return -1; >> } > > This looses diagnostics specificity - is this intended? At least the > out-of-memory condition seems useful to distinguish. Good point. The zstd API no longer exposes the error code enum, but it does expose zstd_get_error_name() which can be used here. I was thinking that the string needed to be static for some reason, but that is not the case. I will make that change. >> +size_t zstd_compress_stream(zstd_cstream *cstream, >> + struct zstd_out_buffer *output, struct zstd_in_buffer *input) >> +{ >> + ZSTD_outBuffer o; >> + ZSTD_inBuffer i; >> + size_t ret; >> + >> + memcpy(&o, output, sizeof(o)); >> + memcpy(&i, input, sizeof(i)); >> + ret = ZSTD_compressStream(cstream, &o, &i); >> + memcpy(output, &o, sizeof(o)); >> + memcpy(input, &i, sizeof(i)); >> + return ret; >> +} > > Is all this copying necessary? How is it different from type-punning by > direct pointer cast? If breaking strict aliasing and type-punning by pointer casing is okay, then we can do that here. These memcpys will be negligible for performance, but type-punning would be more succinct if allowed. Best, Nick
On Thu, Dec 03, 2020 at 01:42:03AM +0000, Nick Terrell wrote: > > > > On Dec 2, 2020, at 5:16 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: > > > > On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote: > >> From: Nick Terrell <terrelln@fb.com> > >> > >> This patch: > >> - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h` > >> - Adds a new API in `include/linux/zstd.h` that is functionally > >> equivalent to the in-use subset of the current API. Functions are > >> renamed to avoid symbol collisions with zstd, to make it clear it is > >> not the upstream zstd API, and to follow the kernel style guide. > >> - Updates all callers to use the new API. > >> > >> There are no functional changes in this patch. Since there are no > >> functional change, I felt it was okay to update all the callers in a > >> single patch, since once the API is approved, the callers are > >> mechanically changed. > > [...] > >> --- a/lib/decompress_unzstd.c > >> +++ b/lib/decompress_unzstd.c > > [...] > >> static int INIT handle_zstd_error(size_t ret, void (*error)(char *x)) > >> { > >> - const int err = ZSTD_getErrorCode(ret); > >> - > >> - if (!ZSTD_isError(ret)) > >> + if (!zstd_is_error(ret)) > >> return 0; > >> > >> - switch (err) { > >> - case ZSTD_error_memory_allocation: > >> - error("ZSTD decompressor ran out of memory"); > >> - break; > >> - case ZSTD_error_prefix_unknown: > >> - error("Input is not in the ZSTD format (wrong magic bytes)"); > >> - break; > >> - case ZSTD_error_dstSize_tooSmall: > >> - case ZSTD_error_corruption_detected: > >> - case ZSTD_error_checksum_wrong: > >> - error("ZSTD-compressed data is corrupt"); > >> - break; > >> - default: > >> - error("ZSTD-compressed data is probably corrupt"); > >> - break; > >> - } > >> + error("ZSTD decompression failed"); > >> return -1; > >> } > > > > This looses diagnostics specificity - is this intended? At least the > > out-of-memory condition seems useful to distinguish. > > Good point. The zstd API no longer exposes the error code enum, > but it does expose zstd_get_error_name() which can be used here. > I was thinking that the string needed to be static for some reason, but > that is not the case. I will make that change. > > >> +size_t zstd_compress_stream(zstd_cstream *cstream, > >> + struct zstd_out_buffer *output, struct zstd_in_buffer *input) > >> +{ > >> + ZSTD_outBuffer o; > >> + ZSTD_inBuffer i; > >> + size_t ret; > >> + > >> + memcpy(&o, output, sizeof(o)); > >> + memcpy(&i, input, sizeof(i)); > >> + ret = ZSTD_compressStream(cstream, &o, &i); > >> + memcpy(output, &o, sizeof(o)); > >> + memcpy(input, &i, sizeof(i)); > >> + return ret; > >> +} > > > > Is all this copying necessary? How is it different from type-punning by > > direct pointer cast? > > If breaking strict aliasing and type-punning by pointer casing is okay, then > we can do that here. These memcpys will be negligible for performance, but > type-punning would be more succinct if allowed. Ah, this might break LTO builds due to strict aliasing violation. So I would suggest to just #define the ZSTD names to kernel ones for the library code. Unless there is a cleaner solution... Best Regards Michał Mirosław
> On Dec 2, 2020, at 7:14 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: > > On Thu, Dec 03, 2020 at 01:42:03AM +0000, Nick Terrell wrote: >> >> >>> On Dec 2, 2020, at 5:16 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: >>> >>> On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote: >>>> From: Nick Terrell <terrelln@fb.com> >>>> >>>> This patch: >>>> - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h` >>>> - Adds a new API in `include/linux/zstd.h` that is functionally >>>> equivalent to the in-use subset of the current API. Functions are >>>> renamed to avoid symbol collisions with zstd, to make it clear it is >>>> not the upstream zstd API, and to follow the kernel style guide. >>>> - Updates all callers to use the new API. >>>> >>>> There are no functional changes in this patch. Since there are no >>>> functional change, I felt it was okay to update all the callers in a >>>> single patch, since once the API is approved, the callers are >>>> mechanically changed. >>> [...] >>>> --- a/lib/decompress_unzstd.c >>>> +++ b/lib/decompress_unzstd.c >>> [...] >>>> static int INIT handle_zstd_error(size_t ret, void (*error)(char *x)) >>>> { >>>> - const int err = ZSTD_getErrorCode(ret); >>>> - >>>> - if (!ZSTD_isError(ret)) >>>> + if (!zstd_is_error(ret)) >>>> return 0; >>>> >>>> - switch (err) { >>>> - case ZSTD_error_memory_allocation: >>>> - error("ZSTD decompressor ran out of memory"); >>>> - break; >>>> - case ZSTD_error_prefix_unknown: >>>> - error("Input is not in the ZSTD format (wrong magic bytes)"); >>>> - break; >>>> - case ZSTD_error_dstSize_tooSmall: >>>> - case ZSTD_error_corruption_detected: >>>> - case ZSTD_error_checksum_wrong: >>>> - error("ZSTD-compressed data is corrupt"); >>>> - break; >>>> - default: >>>> - error("ZSTD-compressed data is probably corrupt"); >>>> - break; >>>> - } >>>> + error("ZSTD decompression failed"); >>>> return -1; >>>> } >>> >>> This looses diagnostics specificity - is this intended? At least the >>> out-of-memory condition seems useful to distinguish. >> >> Good point. The zstd API no longer exposes the error code enum, >> but it does expose zstd_get_error_name() which can be used here. >> I was thinking that the string needed to be static for some reason, but >> that is not the case. I will make that change. >> >>>> +size_t zstd_compress_stream(zstd_cstream *cstream, >>>> + struct zstd_out_buffer *output, struct zstd_in_buffer *input) >>>> +{ >>>> + ZSTD_outBuffer o; >>>> + ZSTD_inBuffer i; >>>> + size_t ret; >>>> + >>>> + memcpy(&o, output, sizeof(o)); >>>> + memcpy(&i, input, sizeof(i)); >>>> + ret = ZSTD_compressStream(cstream, &o, &i); >>>> + memcpy(output, &o, sizeof(o)); >>>> + memcpy(input, &i, sizeof(i)); >>>> + return ret; >>>> +} >>> >>> Is all this copying necessary? How is it different from type-punning by >>> direct pointer cast? >> >> If breaking strict aliasing and type-punning by pointer casing is okay, then >> we can do that here. These memcpys will be negligible for performance, but >> type-punning would be more succinct if allowed. > > Ah, this might break LTO builds due to strict aliasing violation. > So I would suggest to just #define the ZSTD names to kernel ones > for the library code. Unless there is a cleaner solution... I don’t want to do that because I want in the 3rd series of the patchset I update to zstd-1.4.6. And I’m using zstd-1.4.6 as-is in upstream. This allows us to keep the kernel version up to date, since the patch to update to a new version can be generated automatically (and manually tested), so it doesn’t fall years behind upstream again. The alternative would be to make upstream zstd’s header public and #define zstd_in_buffer ZSTD_inBuffer. But that would make zstd’s header public, which would somewhat defeat the purpose of having a kernel wrapper. These memcpy’s won’t hurt performance, since this function is called at most every 4KB of input data in all the callers, though they are clunky.
On Thu, Dec 03, 2020 at 03:59:21AM +0000, Nick Terrell wrote: > On Dec 2, 2020, at 7:14 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: > > On Thu, Dec 03, 2020 at 01:42:03AM +0000, Nick Terrell wrote: > >> On Dec 2, 2020, at 5:16 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: > >>> On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote: > >>>> From: Nick Terrell <terrelln@fb.com> > >>>> > >>>> This patch: > >>>> - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h` > >>>> - Adds a new API in `include/linux/zstd.h` that is functionally > >>>> equivalent to the in-use subset of the current API. Functions are > >>>> renamed to avoid symbol collisions with zstd, to make it clear it is > >>>> not the upstream zstd API, and to follow the kernel style guide. > >>>> - Updates all callers to use the new API. > >>>> > >>>> There are no functional changes in this patch. Since there are no > >>>> functional change, I felt it was okay to update all the callers in a > >>>> single patch, since once the API is approved, the callers are > >>>> mechanically changed. > >>> [...] > >>>> --- a/lib/decompress_unzstd.c > >>>> +++ b/lib/decompress_unzstd.c > >>> [...] > >>>> static int INIT handle_zstd_error(size_t ret, void (*error)(char *x)) > >>>> { > >>>> - const int err = ZSTD_getErrorCode(ret); > >>>> - > >>>> - if (!ZSTD_isError(ret)) > >>>> + if (!zstd_is_error(ret)) > >>>> return 0; > >>>> > >>>> - switch (err) { > >>>> - case ZSTD_error_memory_allocation: > >>>> - error("ZSTD decompressor ran out of memory"); > >>>> - break; > >>>> - case ZSTD_error_prefix_unknown: > >>>> - error("Input is not in the ZSTD format (wrong magic bytes)"); > >>>> - break; > >>>> - case ZSTD_error_dstSize_tooSmall: > >>>> - case ZSTD_error_corruption_detected: > >>>> - case ZSTD_error_checksum_wrong: > >>>> - error("ZSTD-compressed data is corrupt"); > >>>> - break; > >>>> - default: > >>>> - error("ZSTD-compressed data is probably corrupt"); > >>>> - break; > >>>> - } > >>>> + error("ZSTD decompression failed"); > >>>> return -1; > >>>> } > >>> > >>> This looses diagnostics specificity - is this intended? At least the > >>> out-of-memory condition seems useful to distinguish. > >> > >> Good point. The zstd API no longer exposes the error code enum, > >> but it does expose zstd_get_error_name() which can be used here. > >> I was thinking that the string needed to be static for some reason, but > >> that is not the case. I will make that change. > >> > >>>> +size_t zstd_compress_stream(zstd_cstream *cstream, > >>>> + struct zstd_out_buffer *output, struct zstd_in_buffer *input) > >>>> +{ > >>>> + ZSTD_outBuffer o; > >>>> + ZSTD_inBuffer i; > >>>> + size_t ret; > >>>> + > >>>> + memcpy(&o, output, sizeof(o)); > >>>> + memcpy(&i, input, sizeof(i)); > >>>> + ret = ZSTD_compressStream(cstream, &o, &i); > >>>> + memcpy(output, &o, sizeof(o)); > >>>> + memcpy(input, &i, sizeof(i)); > >>>> + return ret; > >>>> +} > >>> > >>> Is all this copying necessary? How is it different from type-punning by > >>> direct pointer cast? > >> > >> If breaking strict aliasing and type-punning by pointer casing is okay, then > >> we can do that here. These memcpys will be negligible for performance, but > >> type-punning would be more succinct if allowed. > > > > Ah, this might break LTO builds due to strict aliasing violation. > > So I would suggest to just #define the ZSTD names to kernel ones > > for the library code. Unless there is a cleaner solution... > > I don’t want to do that because I want in the 3rd series of the patchset I update > to zstd-1.4.6. And I’m using zstd-1.4.6 as-is in upstream. This allows us to keep > the kernel version up to date, since the patch to update to a new version can be > generated automatically (and manually tested), so it doesn’t fall years behind > upstream again. > > The alternative would be to make upstream zstd’s header public and > #define zstd_in_buffer ZSTD_inBuffer. But that would make zstd’s header > public, which would somewhat defeat the purpose of having a kernel wrapper. I thought the problem was API style spill-over from the library to other parts of the kernel. A header-only wrapper can stop this. I'm not sure symbol visibility (namespace pollution) was a concern. Best Regards Michał Mirosław
> On Dec 2, 2020, at 9:03 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: > > On Thu, Dec 03, 2020 at 03:59:21AM +0000, Nick Terrell wrote: >> On Dec 2, 2020, at 7:14 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: >>> On Thu, Dec 03, 2020 at 01:42:03AM +0000, Nick Terrell wrote: >>>> On Dec 2, 2020, at 5:16 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: >>>>> On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote: >>>>>> From: Nick Terrell <terrelln@fb.com> >>>>>> >>>>>> This patch: >>>>>> - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h` >>>>>> - Adds a new API in `include/linux/zstd.h` that is functionally >>>>>> equivalent to the in-use subset of the current API. Functions are >>>>>> renamed to avoid symbol collisions with zstd, to make it clear it is >>>>>> not the upstream zstd API, and to follow the kernel style guide. >>>>>> - Updates all callers to use the new API. >>>>>> >>>>>> There are no functional changes in this patch. Since there are no >>>>>> functional change, I felt it was okay to update all the callers in a >>>>>> single patch, since once the API is approved, the callers are >>>>>> mechanically changed. >>>>> [...] >>>>>> --- a/lib/decompress_unzstd.c >>>>>> +++ b/lib/decompress_unzstd.c >>>>> [...] >>>>>> static int INIT handle_zstd_error(size_t ret, void (*error)(char *x)) >>>>>> { >>>>>> - const int err = ZSTD_getErrorCode(ret); >>>>>> - >>>>>> - if (!ZSTD_isError(ret)) >>>>>> + if (!zstd_is_error(ret)) >>>>>> return 0; >>>>>> >>>>>> - switch (err) { >>>>>> - case ZSTD_error_memory_allocation: >>>>>> - error("ZSTD decompressor ran out of memory"); >>>>>> - break; >>>>>> - case ZSTD_error_prefix_unknown: >>>>>> - error("Input is not in the ZSTD format (wrong magic bytes)"); >>>>>> - break; >>>>>> - case ZSTD_error_dstSize_tooSmall: >>>>>> - case ZSTD_error_corruption_detected: >>>>>> - case ZSTD_error_checksum_wrong: >>>>>> - error("ZSTD-compressed data is corrupt"); >>>>>> - break; >>>>>> - default: >>>>>> - error("ZSTD-compressed data is probably corrupt"); >>>>>> - break; >>>>>> - } >>>>>> + error("ZSTD decompression failed"); >>>>>> return -1; >>>>>> } >>>>> >>>>> This looses diagnostics specificity - is this intended? At least the >>>>> out-of-memory condition seems useful to distinguish. >>>> >>>> Good point. The zstd API no longer exposes the error code enum, >>>> but it does expose zstd_get_error_name() which can be used here. >>>> I was thinking that the string needed to be static for some reason, but >>>> that is not the case. I will make that change. >>>> >>>>>> +size_t zstd_compress_stream(zstd_cstream *cstream, >>>>>> + struct zstd_out_buffer *output, struct zstd_in_buffer *input) >>>>>> +{ >>>>>> + ZSTD_outBuffer o; >>>>>> + ZSTD_inBuffer i; >>>>>> + size_t ret; >>>>>> + >>>>>> + memcpy(&o, output, sizeof(o)); >>>>>> + memcpy(&i, input, sizeof(i)); >>>>>> + ret = ZSTD_compressStream(cstream, &o, &i); >>>>>> + memcpy(output, &o, sizeof(o)); >>>>>> + memcpy(input, &i, sizeof(i)); >>>>>> + return ret; >>>>>> +} >>>>> >>>>> Is all this copying necessary? How is it different from type-punning by >>>>> direct pointer cast? >>>> >>>> If breaking strict aliasing and type-punning by pointer casing is okay, then >>>> we can do that here. These memcpys will be negligible for performance, but >>>> type-punning would be more succinct if allowed. >>> >>> Ah, this might break LTO builds due to strict aliasing violation. >>> So I would suggest to just #define the ZSTD names to kernel ones >>> for the library code. Unless there is a cleaner solution... >> >> I don’t want to do that because I want in the 3rd series of the patchset I update >> to zstd-1.4.6. And I’m using zstd-1.4.6 as-is in upstream. This allows us to keep >> the kernel version up to date, since the patch to update to a new version can be >> generated automatically (and manually tested), so it doesn’t fall years behind >> upstream again. >> >> The alternative would be to make upstream zstd’s header public and >> #define zstd_in_buffer ZSTD_inBuffer. But that would make zstd’s header >> public, which would somewhat defeat the purpose of having a kernel wrapper. > > I thought the problem was API style spill-over from the library to other parts > of the kernel. A header-only wrapper can stop this. I'm not sure symbol > visibility (namespace pollution) was a concern. Thats true. It seems slightly unclean, but so Is duplicating these structs and memcpying them. So I’ll go ahead and expose the upstream zstd’s header (“lib/zstd/zstd.h” here). I’ll just need to pick a name for the upstream “zstd.h” header. > Best Regards > Michał Mirosław
> On Dec 2, 2020, at 9:03 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: > > On Thu, Dec 03, 2020 at 03:59:21AM +0000, Nick Terrell wrote: >> On Dec 2, 2020, at 7:14 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: >>> On Thu, Dec 03, 2020 at 01:42:03AM +0000, Nick Terrell wrote: >>>> On Dec 2, 2020, at 5:16 PM, Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote: >>>>> On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote: >>>>>> From: Nick Terrell <terrelln@fb.com> >>>>>> >>>>>> This patch: >>>>>> - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h` >>>>>> - Adds a new API in `include/linux/zstd.h` that is functionally >>>>>> equivalent to the in-use subset of the current API. Functions are >>>>>> renamed to avoid symbol collisions with zstd, to make it clear it is >>>>>> not the upstream zstd API, and to follow the kernel style guide. >>>>>> - Updates all callers to use the new API. >>>>>> >>>>>> There are no functional changes in this patch. Since there are no >>>>>> functional change, I felt it was okay to update all the callers in a >>>>>> single patch, since once the API is approved, the callers are >>>>>> mechanically changed. >>>>> [...] >>>>>> --- a/lib/decompress_unzstd.c >>>>>> +++ b/lib/decompress_unzstd.c >>>>> [...] >>>>>> static int INIT handle_zstd_error(size_t ret, void (*error)(char *x)) >>>>>> { >>>>>> - const int err = ZSTD_getErrorCode(ret); >>>>>> - >>>>>> - if (!ZSTD_isError(ret)) >>>>>> + if (!zstd_is_error(ret)) >>>>>> return 0; >>>>>> >>>>>> - switch (err) { >>>>>> - case ZSTD_error_memory_allocation: >>>>>> - error("ZSTD decompressor ran out of memory"); >>>>>> - break; >>>>>> - case ZSTD_error_prefix_unknown: >>>>>> - error("Input is not in the ZSTD format (wrong magic bytes)"); >>>>>> - break; >>>>>> - case ZSTD_error_dstSize_tooSmall: >>>>>> - case ZSTD_error_corruption_detected: >>>>>> - case ZSTD_error_checksum_wrong: >>>>>> - error("ZSTD-compressed data is corrupt"); >>>>>> - break; >>>>>> - default: >>>>>> - error("ZSTD-compressed data is probably corrupt"); >>>>>> - break; >>>>>> - } >>>>>> + error("ZSTD decompression failed"); >>>>>> return -1; >>>>>> } >>>>> >>>>> This looses diagnostics specificity - is this intended? At least the >>>>> out-of-memory condition seems useful to distinguish. >>>> >>>> Good point. The zstd API no longer exposes the error code enum, >>>> but it does expose zstd_get_error_name() which can be used here. >>>> I was thinking that the string needed to be static for some reason, but >>>> that is not the case. I will make that change. >>>> >>>>>> +size_t zstd_compress_stream(zstd_cstream *cstream, >>>>>> + struct zstd_out_buffer *output, struct zstd_in_buffer *input) >>>>>> +{ >>>>>> + ZSTD_outBuffer o; >>>>>> + ZSTD_inBuffer i; >>>>>> + size_t ret; >>>>>> + >>>>>> + memcpy(&o, output, sizeof(o)); >>>>>> + memcpy(&i, input, sizeof(i)); >>>>>> + ret = ZSTD_compressStream(cstream, &o, &i); >>>>>> + memcpy(output, &o, sizeof(o)); >>>>>> + memcpy(input, &i, sizeof(i)); >>>>>> + return ret; >>>>>> +} >>>>> >>>>> Is all this copying necessary? How is it different from type-punning by >>>>> direct pointer cast? >>>> >>>> If breaking strict aliasing and type-punning by pointer casing is okay, then >>>> we can do that here. These memcpys will be negligible for performance, but >>>> type-punning would be more succinct if allowed. >>> >>> Ah, this might break LTO builds due to strict aliasing violation. >>> So I would suggest to just #define the ZSTD names to kernel ones >>> for the library code. Unless there is a cleaner solution... >> >> I don’t want to do that because I want in the 3rd series of the patchset I update >> to zstd-1.4.6. And I’m using zstd-1.4.6 as-is in upstream. This allows us to keep >> the kernel version up to date, since the patch to update to a new version can be >> generated automatically (and manually tested), so it doesn’t fall years behind >> upstream again. >> >> The alternative would be to make upstream zstd’s header public and >> #define zstd_in_buffer ZSTD_inBuffer. But that would make zstd’s header >> public, which would somewhat defeat the purpose of having a kernel wrapper. > > I thought the problem was API style spill-over from the library to other parts > of the kernel. A header-only wrapper can stop this. I'm not sure symbol > visibility (namespace pollution) was a concern. Thanks for the review Michał! I have just submitted a new version of the patches with the suggested changes! Best, Nick Terrell > Best Regards > Michał Mirosław
From: Nick Terrell <terrelln@fb.com> Please pull from git@github.com:terrelln/linux.git tags/zstd-1.4.6-v6 to get these changes. Alternatively the patchset is included. This patchset upgrades the zstd library to the latest upstream release. The current zstd version in the kernel is a modified version of upstream zstd-1.3.1. At the time it was integrated, zstd wasn't ready to be used in the kernel as-is. But, it is now possible to use upstream zstd directly in the kernel. I have not yet released zstd-1.4.6 upstream. I want the zstd version in the kernel to match up with a known upstream release, so we know exactly what code is running. Whenever this patchset is ready for merge, I will cut a release at the upstream commit that gets merged. This should not be necessary for future releases. The kernel zstd library is automatically generated from upstream zstd. A script makes the necessary changes and imports it into the kernel. The changes are: 1. Replace all libc dependencies with kernel replacements and rewrite includes. 2. Remove unncessary portability macros like: #if defined(_MSC_VER). 3. Use the kernel xxhash instead of bundling it. This automation gets tested every commit by upstream's continuous integration. When we cut a new zstd release, we will submit a patch to the kernel to update the zstd version in the kernel. I've updated zstd to upstream with one big patch because every commit must build, so that precludes partial updates. Since the commit is 100% generated, I hope the review burden is lightened. I considered replaying upstream commits, but that is not possible because there have been ~3500 upstream commits since the last zstd import, and the commits don't all build individually. The bulk update preserves bisectablity because bugs can be bisected to the zstd version update. At that point the update can be reverted, and we can work with upstream to find and fix the bug. After this big switch in how the kernel consumes zstd, future patches will be smaller, because they will only have one upstream release worth of changes each. This patchset adds a new kernel-style wrapper around zstd. This wrapper API is functionally equivalent to the subset of the current zstd API that is currently used. The wrapper API changes to be kernel style so that the symbols don't collide with zstd's symbols. The update to zstd-1.4.6 maintains the same API and preserves the semantics, so that none of the callers need to be updated. This patchset comes in 2 parts: 1. The first 2 patches prepare for the zstd upgrade. The first patch adds the new kernel style API so zstd can be upgraded without modifying any callers. The second patch adds an indirection for the lib/decompress_unzstd.c including of all decompression source files. 2. Import zstd-1.4.6. This patch is completely generated from upstream using automated tooling. I tested every caller of zstd on x86_64. I tested both after the 1.4.6 upgrade using the compatibility wrapper, and after the final patch in this series. I tested kernel and initramfs decompression in i386 and arm. I ran benchmarks to compare the current zstd in the kernel with zstd-1.4.6. I benchmarked on x86_64 using QEMU with KVM enabled on an Intel i9-9900k. I found: * BtrFS zstd compression at levels 1 and 3 is 5% faster * BtrFS zstd decompression+read is 15% faster * SquashFS zstd decompression+read is 15% faster * F2FS zstd compression+write at level 3 is 8% faster * F2FS zstd decompression+read is 20% faster * ZRAM decompression+read is 30% faster * Kernel zstd decompression is 35% faster * Initramfs zstd decompression+build is 5% faster The latest zstd also offers bug fixes and a 1 KB reduction in stack uage during compression. For example the recent problem with large kernel decompression has been fixed upstream for over 2 years https://lkml.org/lkml/2020/9/29/27. Please let me know if there is anything that I can do to ease the way for these patches. I think it is important because it gets large performance improvements, contains bug fixes, and is switching to a more maintainable model of consuming upstream zstd directly, making it easy to keep up to date. Best, Nick Terrell v1 -> v2: * Successfully tested F2FS with help from Chao Yu to fix my test. * (1/9) Fix ZSTD_initCStream() wrapper to handle pledged_src_size=0 means unknown. This fixes F2FS with the zstd-1.4.6 compatibility wrapper, exposed by the test. v2 -> v3: * (3/9) Silence warnings by Kernel Test Robot: https://github.com/facebook/zstd/pull/2324 Stack size warnings remain, but these aren't new, and the functions it warns on are either unused or not in the maximum stack path. This patchset reduces zstd compression stack usage by 1 KB overall. I've gotten the low hanging fruit, and more stack reduction would require significant changes that have the potential to introduce new bugs. However, I do hope to continue to reduce zstd stack usage in future versions. v3 -> v4: * (3/9) Fix errors and warnings reported by Kernel Test Robot: https://github.com/facebook/zstd/pull/2326 - Replace mem.h with a custom kernel implementation that matches the current lib/zstd/mem.h in the kernel. This avoids calls to __builtin_bswap*() which don't work on certain architectures, as exposed by the Kernel Test Robot. - Remove ASAN/MSAN (un)poisoning code which doesn't work in the kernel, as exposed by the Kernel Test Robot. - I've fixed all of the valid cppcheck warnings reported, but there were many false positives, where cppcheck was incorrectly analyzing the situation, which I did not fix. I don't believe it is reasonable to expect that upstream zstd silences all the static analyzer false positives. Upstream zstd uses clang scan-build for its static analysis. We find that supporting multiple static analysis tools multiplies the burden of silencing false positives, without providing enough marginal value over running a single static analysis tool. v4 -> v5: * Rebase onto v5.10-rc2 * (6/9) Merge with other F2FS changes (no functional change in patch). v5 -> v6: * Rebase onto v5.10-rc6. * Switch to using a kernel style wrapper API as suggested by Cristoph. Nick Terrell (3): lib: zstd: Add kernel-specific API lib: zstd: Add decompress_sources.h for decompress_unzstd lib: zstd: Upgrade to latest upstream zstd version 1.4.6 crypto/zstd.c | 28 +- fs/btrfs/zstd.c | 72 +- fs/f2fs/compress.c | 56 +- fs/pstore/platform.c | 2 +- fs/squashfs/zstd_wrapper.c | 16 +- include/linux/zstd.h | 1274 ++--- lib/decompress_unzstd.c | 66 +- lib/zstd/Makefile | 35 +- lib/zstd/bitstream.h | 379 -- lib/zstd/common/bitstream.h | 437 ++ lib/zstd/common/compiler.h | 150 + lib/zstd/common/cpu.h | 194 + lib/zstd/common/debug.c | 24 + lib/zstd/common/debug.h | 101 + lib/zstd/common/entropy_common.c | 355 ++ lib/zstd/common/error_private.c | 55 + lib/zstd/common/error_private.h | 66 + lib/zstd/common/fse.h | 709 +++ lib/zstd/common/fse_decompress.c | 380 ++ lib/zstd/common/huf.h | 352 ++ lib/zstd/common/mem.h | 258 + lib/zstd/common/zstd_common.c | 83 + lib/zstd/common/zstd_deps.h | 124 + lib/zstd/common/zstd_errors.h | 76 + lib/zstd/common/zstd_internal.h | 438 ++ lib/zstd/compress.c | 3485 -------------- lib/zstd/compress/fse_compress.c | 625 +++ lib/zstd/compress/hist.c | 165 + lib/zstd/compress/hist.h | 75 + lib/zstd/compress/huf_compress.c | 764 +++ lib/zstd/compress/zstd_compress.c | 4157 +++++++++++++++++ lib/zstd/compress/zstd_compress_internal.h | 1103 +++++ lib/zstd/compress/zstd_compress_literals.c | 158 + lib/zstd/compress/zstd_compress_literals.h | 29 + lib/zstd/compress/zstd_compress_sequences.c | 433 ++ lib/zstd/compress/zstd_compress_sequences.h | 54 + lib/zstd/compress/zstd_compress_superblock.c | 849 ++++ lib/zstd/compress/zstd_compress_superblock.h | 32 + lib/zstd/compress/zstd_cwksp.h | 465 ++ lib/zstd/compress/zstd_double_fast.c | 521 +++ lib/zstd/compress/zstd_double_fast.h | 32 + lib/zstd/compress/zstd_fast.c | 496 ++ lib/zstd/compress/zstd_fast.h | 31 + lib/zstd/compress/zstd_lazy.c | 1138 +++++ lib/zstd/compress/zstd_lazy.h | 61 + lib/zstd/compress/zstd_ldm.c | 619 +++ lib/zstd/compress/zstd_ldm.h | 104 + lib/zstd/compress/zstd_opt.c | 1200 +++++ lib/zstd/compress/zstd_opt.h | 50 + lib/zstd/decompress.c | 2531 ---------- lib/zstd/decompress/huf_decompress.c | 1205 +++++ lib/zstd/decompress/zstd_ddict.c | 241 + lib/zstd/decompress/zstd_ddict.h | 44 + lib/zstd/decompress/zstd_decompress.c | 1836 ++++++++ lib/zstd/decompress/zstd_decompress_block.c | 1540 ++++++ lib/zstd/decompress/zstd_decompress_block.h | 62 + .../decompress/zstd_decompress_internal.h | 195 + lib/zstd/decompress_sources.h | 19 + lib/zstd/entropy_common.c | 243 - lib/zstd/error_private.h | 53 - lib/zstd/fse.h | 575 --- lib/zstd/fse_compress.c | 795 ---- lib/zstd/fse_decompress.c | 325 -- lib/zstd/huf.h | 212 - lib/zstd/huf_compress.c | 772 --- lib/zstd/huf_decompress.c | 960 ---- lib/zstd/mem.h | 151 - lib/zstd/zstd.h | 2104 +++++++++ lib/zstd/zstd_common.c | 75 - lib/zstd/zstd_compress_module.c | 206 + lib/zstd/zstd_decompress_module.c | 122 + lib/zstd/zstd_internal.h | 273 -- lib/zstd/zstd_opt.h | 1014 ---- 73 files changed, 24966 insertions(+), 12963 deletions(-) delete mode 100644 lib/zstd/bitstream.h create mode 100644 lib/zstd/common/bitstream.h create mode 100644 lib/zstd/common/compiler.h create mode 100644 lib/zstd/common/cpu.h create mode 100644 lib/zstd/common/debug.c create mode 100644 lib/zstd/common/debug.h create mode 100644 lib/zstd/common/entropy_common.c create mode 100644 lib/zstd/common/error_private.c create mode 100644 lib/zstd/common/error_private.h create mode 100644 lib/zstd/common/fse.h create mode 100644 lib/zstd/common/fse_decompress.c create mode 100644 lib/zstd/common/huf.h create mode 100644 lib/zstd/common/mem.h create mode 100644 lib/zstd/common/zstd_common.c create mode 100644 lib/zstd/common/zstd_deps.h create mode 100644 lib/zstd/common/zstd_errors.h create mode 100644 lib/zstd/common/zstd_internal.h delete mode 100644 lib/zstd/compress.c create mode 100644 lib/zstd/compress/fse_compress.c create mode 100644 lib/zstd/compress/hist.c create mode 100644 lib/zstd/compress/hist.h create mode 100644 lib/zstd/compress/huf_compress.c create mode 100644 lib/zstd/compress/zstd_compress.c create mode 100644 lib/zstd/compress/zstd_compress_internal.h create mode 100644 lib/zstd/compress/zstd_compress_literals.c create mode 100644 lib/zstd/compress/zstd_compress_literals.h create mode 100644 lib/zstd/compress/zstd_compress_sequences.c create mode 100644 lib/zstd/compress/zstd_compress_sequences.h create mode 100644 lib/zstd/compress/zstd_compress_superblock.c create mode 100644 lib/zstd/compress/zstd_compress_superblock.h create mode 100644 lib/zstd/compress/zstd_cwksp.h create mode 100644 lib/zstd/compress/zstd_double_fast.c create mode 100644 lib/zstd/compress/zstd_double_fast.h create mode 100644 lib/zstd/compress/zstd_fast.c create mode 100644 lib/zstd/compress/zstd_fast.h create mode 100644 lib/zstd/compress/zstd_lazy.c create mode 100644 lib/zstd/compress/zstd_lazy.h create mode 100644 lib/zstd/compress/zstd_ldm.c create mode 100644 lib/zstd/compress/zstd_ldm.h create mode 100644 lib/zstd/compress/zstd_opt.c create mode 100644 lib/zstd/compress/zstd_opt.h delete mode 100644 lib/zstd/decompress.c create mode 100644 lib/zstd/decompress/huf_decompress.c create mode 100644 lib/zstd/decompress/zstd_ddict.c create mode 100644 lib/zstd/decompress/zstd_ddict.h create mode 100644 lib/zstd/decompress/zstd_decompress.c create mode 100644 lib/zstd/decompress/zstd_decompress_block.c create mode 100644 lib/zstd/decompress/zstd_decompress_block.h create mode 100644 lib/zstd/decompress/zstd_decompress_internal.h create mode 100644 lib/zstd/decompress_sources.h delete mode 100644 lib/zstd/entropy_common.c delete mode 100644 lib/zstd/error_private.h delete mode 100644 lib/zstd/fse.h delete mode 100644 lib/zstd/fse_compress.c delete mode 100644 lib/zstd/fse_decompress.c delete mode 100644 lib/zstd/huf.h delete mode 100644 lib/zstd/huf_compress.c delete mode 100644 lib/zstd/huf_decompress.c delete mode 100644 lib/zstd/mem.h create mode 100644 lib/zstd/zstd.h delete mode 100644 lib/zstd/zstd_common.c create mode 100644 lib/zstd/zstd_compress_module.c create mode 100644 lib/zstd/zstd_decompress_module.c delete mode 100644 lib/zstd/zstd_internal.h delete mode 100644 lib/zstd/zstd_opt.h