On Fri, 2006-11-17 at 11:31 +0000, moreau francis wrote: > Hmm, I'm probably missing something but I don't see what. Please be > nice even if the question is really stupid ;) > > I'm looking at mmap.c code and to understand it I decided to implement > a dumb char device that implement its own foo_mmap() method. In this > method it defined its own vma ops: > > static void foo_vma_open(struct vm_area_struct *vma) > static void foo_vma_close(struct vm_area_struct *vma) > > A dumb application mmap the device in order to make foo_mmap() install > the vma ops. > > mmap(NULL, 16384, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); > > mmap returned 0x2aaae000 for example. Until now, foo_vma_open() and > foo_vma_close() are not called. > > Now I want to unmap the first part of the previous mapping to see how > vma ops are called. So I did: > > munmap(0x2aaae000, 1024); > > and here's what happen: > > foo_vma_open(vma) is called with: > vma->vm_start = 0x2aaae000 > vma->vm_end = 0x2aaaf000 > > foo_vma_close(vma) is called with: > vma->vm_start = 0x2aaae000 > vma->vm_end = 0x2aaaf000 > > However I would have expected: > > foo_vma_open(vma) is called with: > vma->vm_start = 0x2aaaf000 > vma->vm_end = 0x2aaab2000 > > foo_vma_close(vma) is called with: > vma->vm_start = 0x2aaae000 > vma->vm_end = 0x2aaaf000 > > Can anybody tell me why I get this behaviour ? >
http://lwn.net/Kernel/LDD3/ Chapter 15. Section 'Virtual Memory Areas'. Basically; vm_ops->open() is not called on the first vma. With this munmap() you split the area in two, and it so happens the new vma is the lower one. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
