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| author | Arnd Bergmann <arnd@arndb.de> | 2016-03-16 17:39:17 +0100 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2016-03-18 20:29:58 +0100 |
| commit | ef3fb2422ffe92ead0579c21a02095b329434900 (patch) | |
| tree | 7ec167e9ce2e8681ec3d412ddcbbfffc64a8531f /include | |
| parent | fnic: move printk()s outside of the critical code section. (diff) | |
| download | linux-ef3fb2422ffe92ead0579c21a02095b329434900.tar.xz linux-ef3fb2422ffe92ead0579c21a02095b329434900.zip | |
scsi: fc: use get/put_unaligned64 for wwn access
A bug in the gcc-6.0 prerelease version caused at least one
driver (lpfc) to have excessive stack usage when dealing with
wwn data, on the ARM architecture.
lpfc_scsi.c: In function 'lpfc_find_next_oas_lun':
lpfc_scsi.c:117:1: warning: the frame size of 1152 bytes is larger than 1024 bytes [-Wframe-larger-than=]
I have reported this as a gcc regression in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70232
However, using a better implementation of wwn_to_u64() not only
helps with the particular gcc problem but also leads to better
object code for any version or architecture.
The kernel already provides get_unaligned_be64() and
put_unaligned_be64() helper functions that provide an
optimized implementation with the desired semantics.
The lpfc_find_next_oas_lun() function in the example that
grew from 1146 bytes to 5144 bytes when moving from gcc-5.3
to gcc-6.0 is now 804 bytes, as the optimized
get_unaligned_be64() load can be done in three instructions.
The stack usage is now down to 28 bytes from 128 bytes with
gcc-5.3 before.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/scsi/scsi_transport_fc.h | 15 |
1 files changed, 3 insertions, 12 deletions
diff --git a/include/scsi/scsi_transport_fc.h b/include/scsi/scsi_transport_fc.h index 784bc2c0929f..bf66ea6bed2b 100644 --- a/include/scsi/scsi_transport_fc.h +++ b/include/scsi/scsi_transport_fc.h @@ -28,6 +28,7 @@ #define SCSI_TRANSPORT_FC_H #include <linux/sched.h> +#include <asm/unaligned.h> #include <scsi/scsi.h> #include <scsi/scsi_netlink.h> @@ -797,22 +798,12 @@ fc_remote_port_chkready(struct fc_rport *rport) static inline u64 wwn_to_u64(u8 *wwn) { - return (u64)wwn[0] << 56 | (u64)wwn[1] << 48 | - (u64)wwn[2] << 40 | (u64)wwn[3] << 32 | - (u64)wwn[4] << 24 | (u64)wwn[5] << 16 | - (u64)wwn[6] << 8 | (u64)wwn[7]; + return get_unaligned_be64(wwn); } static inline void u64_to_wwn(u64 inm, u8 *wwn) { - wwn[0] = (inm >> 56) & 0xff; - wwn[1] = (inm >> 48) & 0xff; - wwn[2] = (inm >> 40) & 0xff; - wwn[3] = (inm >> 32) & 0xff; - wwn[4] = (inm >> 24) & 0xff; - wwn[5] = (inm >> 16) & 0xff; - wwn[6] = (inm >> 8) & 0xff; - wwn[7] = inm & 0xff; + put_unaligned_be64(inm, wwn); } /** |