swap: do not send discards as barriers
swap: do not send discards as barriers

The swap code already uses synchronous discards, no need to add I/O
barriers.

This fixes the worst of the terrible slowdown in swap allocation for
hibernation, reported on 2.6.35 by Nigel Cunningham; but does not entirely
eliminate that regression.

[546b05909706652891a87f7bfe385ae147f61f91@kernel.org: superflous newlines removed]
Signed-off-by: Christoph Hellwig <923f7720577207a44b32e59bbfbea59d27f1ae8e@lst.de>
Tested-by: Nigel Cunningham <cfea2496442c091fddd1ba215d62a69ec34e94d0@tuxonice.net>
Signed-off-by: Tejun Heo <546b05909706652891a87f7bfe385ae147f61f91@kernel.org>
Signed-off-by: Hugh Dickins <d3abdf3e2800e6cb849f11b81e6eb50b34d96431@google.com>
Cc: Jens Axboe <08e836a620179c237f631ad0545a7ebdf54201f3@fusionio.com>
Cc: James Bottomley <407b36959ca09543ccda8f8e06721c791bc53435@hansenpartnership.com>
Cc: "Martin K. Petersen" <0384aaef27f06874adbdb09a807bb339f4aff9fd@oracle.com>
Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@kernel.org>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas