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dax: improve comment about truncate race

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Jan Kara pointed out I should be more explicit here about the perils of
racing against truncate.  The comment is mostly the same as for the PTE
case.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2015-09-08 14:59:17 -07:00 committed by Linus Torvalds
parent ae18d6dcf5
commit 84c4e5e675
1 changed files with 6 additions and 1 deletions
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7
fs/dax.c
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@ -553,7 +553,12 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
goto fallback; goto fallback;
/* Guard against a race with truncate */ /*
* If a truncate happened while we were allocating blocks, we may
* leave blocks allocated to the file that are beyond EOF. We can't
* take i_mutex here, so just leave them hanging; they'll be freed
* when the file is deleted.
*/
size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (pgoff >= size) { if (pgoff >= size) {
result = VM_FAULT_SIGBUS; result = VM_FAULT_SIGBUS;