test/osd: fix buffer alignment issue in unittest_ecbackend#66849
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test/osd: fix buffer alignment issue in unittest_ecbackend#66849
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@aainscow hi Alex, could you please help review this change? |
The create_buf() function in TestECBackend.cc had two issues that caused test failures when running with ASan enabled: 1. Infinite loop potential: When std::rand() % 5 returned 0, len_to_add would be 0, causing an infinite loop if the buffer hadn't reached the target length yet. 2. Memory alignment issue: Using append_zero() doesn't guarantee that the resulting buffer's memory address is aligned to EC_ALIGN_SIZE (4096 bytes). The is_aligned() check verifies that all buffers in the bufferlist have their data pointers properly aligned, not just that the length is a multiple of the alignment size. Fix by: - Changing std::rand() % 5 to std::rand() % 5 + 1 to ensure we always allocate 1-5 pages worth of data, avoiding the infinite loop - Replacing append_zero() with buffer::create_page_aligned() followed by memset() and append(), which ensures each buffer has its data pointer aligned to page boundaries (4096 bytes) This ensures the test passes consistently with ASan enabled. Signed-off-by: Kefu Chai <k.chai@proxmox.com>
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the failure manifests when testing with ASan enabled. it looks like: |
aainscow
reviewed
Jan 9, 2026
| uint64_t pages = std::rand() % 5 + 1; // 1-5 pages to avoid infinite loop | ||
| uint64_t len_to_add = std::min(len - bl.length(), pages * EC_ALIGN_SIZE); | ||
| bl.append_zero(len_to_add); | ||
| // Create page-aligned buffer to ensure memory alignment |
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I wonder if we should really fix bl.append_zero() so that it create page aligned buffers by default.
Clearly that would be a more intrusive change, so I am going to approve this change.
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Yes, I don't dare to "fix" append_zero(), hence changed the test instead.
aainscow
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Jan 9, 2026
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Thanks for the fix. LGTM. |
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The create_buf() function in TestECBackend.cc had two issues that caused test failures when running with ASan enabled:
std::rand() % 5returned 0, len_to_add would be 0, causing an infinite loop if the buffer hadn't reached the target length yet.EC_ALIGN_SIZE(4096 bytes). The is_aligned() check verifies that all buffers in the bufferlist have their data pointers properly aligned, not just that the length is a multiple of the alignment size.Fix by:
std::rand() % 5tostd::rand() % 5 + 1to ensure we always allocate 1-5 pages worth of data, avoiding the infinite loopappend_zero()withbuffer::create_page_aligned()followed bymemset()andappend(), which ensures each buffer has its data pointer aligned to page boundaries (4096 bytes)This ensures the test passes consistently with ASan enabled.
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