David Sterba
2011-Mar-18 15:28 UTC
[PATCH] btrfs: properly access unaligned checksum buffer
fixes https://bugzilla.kernel.org/show_bug.cgi?id=29142
reported on SPARC64, warnings like:
[ 1523.941667] Kernel unaligned access at TPC[100e4034]
btrfs_csum_final+0x38/0x3c [btrfs]
Reported-by: Adrien Dessemond <adrien.dessemond@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Tested-by: Adrien Dessemond <adrien.dessemond@gmail.com>
---
fs/btrfs/disk-io.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e1aa8d6..8065863 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -198,7 +198,11 @@ u32 btrfs_csum_data(struct btrfs_root *root, char *data,
u32 seed, size_t len)
void btrfs_csum_final(u32 crc, char *result)
{
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
*(__le32 *)result = ~cpu_to_le32(crc);
+#else
+ put_unaligned_le32(~crc, result);
+#endif
}
/*
--
1.7.4.1.176.g501cc
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Chris Mason
2011-Mar-18 15:56 UTC
Re: [PATCH] btrfs: properly access unaligned checksum buffer
Excerpts from David Sterba''s message of 2011-03-18 11:28:25 -0400:> fixes https://bugzilla.kernel.org/show_bug.cgi?id=29142 > reported on SPARC64, warnings like: > > [ 1523.941667] Kernel unaligned access at TPC[100e4034] > btrfs_csum_final+0x38/0x3c [btrfs] > > Reported-by: Adrien Dessemond <adrien.dessemond@gmail.com> > Signed-off-by: David Sterba <dsterba@suse.cz> > Tested-by: Adrien Dessemond <adrien.dessemond@gmail.com> > --- > fs/btrfs/disk-io.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index e1aa8d6..8065863 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -198,7 +198,11 @@ u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len) > > void btrfs_csum_final(u32 crc, char *result) > { > +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > *(__le32 *)result = ~cpu_to_le32(crc); > +#else > + put_unaligned_le32(~crc, result); > +#endif > }Thanks for fielding this one. Does put_unaligned_le32 optimize away on platforms with efficient access? It would be great if we didn''t need the #ifdef. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
David Sterba
2011-Mar-18 22:56 UTC
Re: [PATCH] btrfs: properly access unaligned checksum buffer
On Fri, Mar 18, 2011 at 11:56:53AM -0400, Chris Mason wrote:> Thanks for fielding this one. Does put_unaligned_le32 optimize away on > platforms with efficient access? It would be great if we didn''t need > the #ifdef.(quicktest: assembly output is same for put_unaligned_le32 and direct assignment on my x86_64) I was originally following examples in Documentation/unaligned-memory-access.txt. From other code it seems to me that the define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is intended for larger portions of code. Macros/wrappers for {put,get}_unaligned* are chosen via arch/<arch>/include/asm/unaligned.h accordingly, therefore it''s safe to use put_unaligned_le32 without the ifdef. dave -- From: David Sterba <dsterba@suse.cz> fixes https://bugzilla.kernel.org/show_bug.cgi?id=29142 reported on SPARC64, warnings like: [ 1523.941667] Kernel unaligned access at TPC[100e4034] btrfs_csum_final+0x38/0x3c [btrfs] Reported-by: Adrien Dessemond <adrien.dessemond@gmail.com> Signed-off-by: David Sterba <dsterba@suse.cz> Tested-by: Adrien Dessemond <adrien.dessemond@gmail.com> --- fs/btrfs/disk-io.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index e1aa8d6..80a6830 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -29,6 +29,7 @@ #include <linux/crc32c.h> #include <linux/slab.h> #include <linux/migrate.h> +#include <asm/unaligned.h> #include "compat.h" #include "ctree.h" #include "disk-io.h" @@ -198,7 +199,7 @@ u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len) void btrfs_csum_final(u32 crc, char *result) { - *(__le32 *)result = ~cpu_to_le32(crc); + put_unaligned_le32(~crc, result); } /* -- 1.7.4.1.176.g501cc -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html