Marek,
I am running a CMA test where I keep allocating from a CMA region as long as the allocation fails due to lack of space.
However, I am seeing failures much before I expect them to happen. When the allocation fails, I see a warning coming from __alloc_contig_range(), because test_pages_isolated() returned "true".
The new retry code does try a new range and eventually succeeds.
+static int __alloc_contig_migrate_range(unsigned long start, unsigned long end) +{
+done:
- /* Make sure all pages are isolated. */
- if (!ret) {
- lru_add_drain_all();
- drain_all_pages();
- if (WARN_ON(test_pages_isolated(start, end)))
- ret = -EBUSY;
- }
I tried to find out why this happened and added in a debug print inside __test_page_isolated_in_pageblock(). Here's the resulting log ..
--- [ 133.563140] !!! Found unexpected page(pfn=9aaab), (count=0), (isBuddy=no), (private=0x00000004), (flags=0x00000000), (_mapcount=0) !!! [ 133.576690] ------------[ cut here ]------------ [ 133.582489] WARNING: at mm/page_alloc.c:5804 alloc_contig_range+0x1a4/0x2c4() [ 133.594757] [<c003e814>] (unwind_backtrace+0x0/0xf0) from [<c0079c7c>] (warn_slowpath_common+0x4c/0x64) [ 133.605468] [<c0079c7c>] (warn_slowpath_common+0x4c/0x64) from [<c0079cac>] (warn_slowpath_null+0x18/0x1c) [ 133.616424] [<c0079cac>] (warn_slowpath_null+0x18/0x1c) from [<c00e0e84>] (alloc_contig_range+0x1a4/0x2c4) [ 133.627471] EXT4-fs (mmcblk0p25): re-mounted. Opts: (null) [ 133.633728] [<c00e0e84>] (alloc_contig_range+0x1a4/0x2c4) from [<c0266690>] (dma_alloc_from_contiguous+0x114/0x1c8) [ 133.697113] !!! Found unexpected page(pfn=9aaac), (count=0), (isBuddy=no), (private=0x00000004), (flags=0x00000000), (_mapcount=0) !!! [ 133.710510] EXT4-fs (mmcblk0p26): re-mounted. Opts: (null) [ 133.716766] ------------[ cut here ]------------ [ 133.721954] WARNING: at mm/page_alloc.c:5804 alloc_contig_range+0x1a4/0x2c4() [ 133.734100] Emergency Remount complete [ 133.742584] [<c003e814>] (unwind_backtrace+0x0/0xf0) from [<c0079c7c>] (warn_slowpath_common+0x4c/0x64) [ 133.753448] [<c0079c7c>] (warn_slowpath_common+0x4c/0x64) from [<c0079cac>] (warn_slowpath_null+0x18/0x1c) [ 133.764373] [<c0079cac>] (warn_slowpath_null+0x18/0x1c) from [<c00e0e84>] (alloc_contig_range+0x1a4/0x2c4) [ 133.775299] [<c00e0e84>] (alloc_contig_range+0x1a4/0x2c4) from [<c0266690>] (dma_alloc_from_contiguous+0x114/0x1c8) ---
From the log it looks like the warning showed up because page->private
is set to MIGRATE_CMA instead of MIGRATE_ISOLATED. I've also had a test case where it failed because (page_count() != 0)
Have you or anyone else seen this during the CMA testing?
Also, could this be because we are finding a page within (start, end) that actually belongs to a higher order Buddy block ?
Thanks, Sandeep