From 960cdd09dcabe5e125d8ee1c54fcc1f908e8ef11 Mon Sep 17 00:00:00 2001 From: Pete Zaitcev Date: Tue, 23 May 2017 17:45:43 -0600 Subject: Stop using ceill() to compute padded data size The well-known idiom to compute a required number of data blocks of size B to contain data of length d is: (d + (B-1))/B The code we use, with ceill(), computes the same value, but does it in an unorthodox way. This makes a reviewer to doubt himself and even run tests to make sure we're really computing the obvious thing. Apropos the reviewer confusion, the code in Phazr.IO looks weird. It uses (word_size - hamming_distance) to compute the necessary number of blocks... but then returns the amount of memory needed to store blocks of a different size (word_size). We left all of it alone and return exactly the same values that the old computation returned. All these computations were the only thing in the code that used -lm, so drop that too. Coincidentially, this patch solves the crash of distro-built packages of liberasurecode (see Red Hat bug #1454543). But it's a side effect. Expect a proper patch soon. Change-Id: Ib297f6df304abf5ca8c27d3392b1107a525e0be0 --- src/backends/phazrio/libphazr.c | 2 +- src/erasurecode.c | 8 ++++---- src/erasurecode_helpers.c | 4 ++-- 3 files changed, 7 insertions(+), 7 deletions(-) (limited to 'src') diff --git a/src/backends/phazrio/libphazr.c b/src/backends/phazrio/libphazr.c index 74ad8ad..41ed74e 100644 --- a/src/backends/phazrio/libphazr.c +++ b/src/backends/phazrio/libphazr.c @@ -88,7 +88,7 @@ struct libphazr_descriptor { static int get_padded_blocksize(int w, int hd, int blocksize) { int word_size = w / 8; - return (int) ceill((double) blocksize / (word_size - hd)) * word_size; + return ((blocksize + ((word_size - hd) - 1)) / (word_size - hd)) * word_size; } static int pio_matrix_encode(void *desc, char **data, char **parity, int blocksize) diff --git a/src/erasurecode.c b/src/erasurecode.c index fb6d5de..d4a06c2 100644 --- a/src/erasurecode.c +++ b/src/erasurecode.c @@ -1194,8 +1194,8 @@ int liberasurecode_verify_stripe_metadata(int desc, /** * This computes the aligned size of a buffer passed into * the encode function. The encode function must pad fragments - * to be algined with the word size (w) and the last fragment also - * needs to be aligned. This computes the sum of the algined fragment + * to be aligned with the word size (w) and the last fragment also + * needs to be aligned. This computes the sum of the aligned fragment * sizes for a given buffer to encode. */ int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len) @@ -1218,8 +1218,8 @@ int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len) alignment_multiple = k * word_size; - ret = (int) ceill( (double) - data_len / alignment_multiple) * alignment_multiple; + ret = ((data_len + alignment_multiple - 1) / alignment_multiple) + * alignment_multiple; out: return ret; diff --git a/src/erasurecode_helpers.c b/src/erasurecode_helpers.c index 40db93c..fd14298 100644 --- a/src/erasurecode_helpers.c +++ b/src/erasurecode_helpers.c @@ -199,8 +199,8 @@ int get_aligned_data_size(ec_backend_t instance, int data_len) alignment_multiple = k * word_size; } - aligned_size = (int) - ceill((double) data_len / alignment_multiple) * alignment_multiple; + aligned_size = ((data_len + alignment_multiple - 1) / alignment_multiple) + * alignment_multiple; return aligned_size; } -- cgit v1.2.1