Messages in this thread Patch in this message | | | Date | Sun, 27 Sep 2015 01:02:16 +0200 | From | angelo <> | Subject | [PATCH] mm: fix cpu hangs on truncating last page of a 16t sparse file |
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Hi all,
running xfstests, generic 308 on whatever 32bit arch is possible to observe cpu to hang near 100% on unlink. The test removes a sparse file of length 16tera where only the last 4096 bytes block is mapped. At line 265 of truncate.c there is a if (index >= end) break; But if index is, as in this case, a 4294967295, it match -1 used as eof. Hence the cpu loops 100% just after.
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On 32bit archs, with CONFIG_LBDAF=y, if truncating last page of a 16tera file, "index" variable is set to 4294967295, and hence matches with -1 used as EOF value. This result in an inifite loop when unlink is executed on this file.
Signed-off-by: Angelo Dureghello <angelo@sysam.it> --- mm/truncate.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/truncate.c b/mm/truncate.c index 76e35ad..3751034 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -283,14 +283,15 @@ void truncate_inode_pages_range(struct address_space *mapping, pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); cond_resched(); - index++; + if (index < end) + index++; }
if (partial_start) { struct page *page = find_lock_page(mapping, start - 1); if (page) { unsigned int top = PAGE_CACHE_SIZE; - if (start > end) { + if (start > end && end != -1) { /* Truncation within a single page */ top = partial_end; partial_end = 0; @@ -322,7 +323,7 @@ void truncate_inode_pages_range(struct address_space *mapping, * If the truncation happened within a single page no pages * will be released, just zeroed, so we can bail out now. */ - if (start >= end) + if (start >= end && end != -1) return;
index = start; @@ -337,7 +338,7 @@ void truncate_inode_pages_range(struct address_space *mapping, index = start; continue; } - if (index == start && indices[0] >= end) { + if (index == start && (indices[0] >= end && end != -1)) { /* All gone out of hole to be punched, we're done */ pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); @@ -348,7 +349,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
/* We rely upon deletion not changing page->index */ index = indices[i]; - if (index >= end) { + if (index >= end && (end != -1)) { /* Restart punch to make sure all gone */ index = start - 1; break; -- 2.5.3
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