Messages in this thread | | | Date | Wed, 14 May 2003 00:52:10 +0200 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] Fix for vma merging refcounting bug |
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On Sun, May 11, 2003 at 09:04:06PM +0100, Stephen C. Tweedie wrote: > Hi, > > On Sat, 2003-05-10 at 17:33, Andrea Arcangeli wrote: > > On Fri, May 09, 2003 at 01:34:21PM +0100, Stephen C. Tweedie wrote: > > > When a new vma can be merged simultaneously with its two immediate > > > neighbours in both directions, vma_merge() extends the predecessor vma > > > and deletes the successor. However, if the vma maps a file, it fails to > > > fput() when doing the delete, leaving the file's refcount inconsistent. > > > great catch! nobody could notice it in practice > > Yep --- I only noticed it because I was running a quick-and-dirty vma > merging test and wanted to test on a shmfs file, and noticed that the > temporary shmfs filesystem became unmountable afterwards. Test > attached, in case anybody is interested (it's the third test, mapping a > file page by page in two interleaved passes, which triggers this case.) > > > I'm attaching for review what I'm applying to my -aa tree, to fix the > > above and the other issue with the non-ram vma merging fixed in 2.5. > > Looks OK.
actually I just noticed the fput is never been buggy in my tree:
if (!file || !rb_parent || !vma_merge(mm, prev, rb_parent, addr, addr + len, vma->vm_flags, file, pgoff)) { vma_link(mm, vma, prev, rb_link, rb_parent); if (correct_wcount) atomic_inc(&file->f_dentry->d_inode->i_writecount); } else { if (file) { if (correct_wcount) atomic_inc(&file->f_dentry->d_inode->i_writecount); fput(file); ^^^^^^^^^ } kmem_cache_free(vm_area_cachep, vma); }
so this was a merging bug in 2.5
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