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[PATCH] sg: use compound pages

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sg increments the refcount of constituent pages in its higher order memory
allocations when they are about to be mapped by userspace.  This is done so
the subsequent get_page/put_page when doing the mapping and unmapping does not
free the page.

Move over to the preferred way, that is, using compound pages instead.  This
fixes a whole class of possible obscure bugs where a get_user_pages on a
constituent page may outlast the user mappings or even the driver.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Douglas Gilbert <dougg@torque.net>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2006-03-22 00:08:30 -08:00 committed by Linus Torvalds
parent a6f563db09
commit f9aed0e253
1 changed files with 3 additions and 34 deletions
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37
drivers/scsi/sg.c
View file

@ -1140,32 +1140,6 @@ sg_fasync(int fd, struct file *filp, int mode)
return (retval < 0) ? retval : 0;
}
/* When startFinish==1 increments page counts for pages other than the
first of scatter gather elements obtained from alloc_pages().
When startFinish==0 decrements ... */
static void
sg_rb_correct4mmap(Sg_scatter_hold * rsv_schp, int startFinish)
{
struct scatterlist *sg = rsv_schp->buffer;
struct page *page;
int k, m;
SCSI_LOG_TIMEOUT(3, printk("sg_rb_correct4mmap: startFinish=%d, scatg=%d\n",
startFinish, rsv_schp->k_use_sg));
/* N.B. correction _not_ applied to base page of each allocation */
for (k = 0; k < rsv_schp->k_use_sg; ++k, ++sg) {
for (m = PAGE_SIZE; m < sg->length; m += PAGE_SIZE) {
page = sg->page;
if (startFinish)
get_page(page);
else {
if (page_count(page) > 0)
__put_page(page);
}
}
}
}
static struct page *
sg_vma_nopage(struct vm_area_struct *vma, unsigned long addr, int *type)
{
@ -1237,10 +1211,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
sa += len;
}
if (0 == sfp->mmap_called) {
sg_rb_correct4mmap(rsv_schp, 1); /* do only once per fd lifetime */
sfp->mmap_called = 1;
}
sfp->mmap_called = 1;
vma->vm_flags |= VM_RESERVED;
vma->vm_private_data = sfp;
vma->vm_ops = &sg_mmap_vm_ops;
@ -2395,8 +2366,6 @@ __sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp)
SCSI_LOG_TIMEOUT(6,
printk("__sg_remove_sfp: bufflen=%d, k_use_sg=%d\n",
(int) sfp->reserve.bufflen, (int) sfp->reserve.k_use_sg));
if (sfp->mmap_called)
sg_rb_correct4mmap(&sfp->reserve, 0); /* undo correction */
sg_remove_scat(&sfp->reserve);
}
sfp->parentdp = NULL;
@ -2478,9 +2447,9 @@ sg_page_malloc(int rqSz, int lowDma, int *retSzp)
return resp;
if (lowDma)
page_mask = GFP_ATOMIC | GFP_DMA | __GFP_NOWARN;
page_mask = GFP_ATOMIC | GFP_DMA | __GFP_COMP | __GFP_NOWARN;
else
page_mask = GFP_ATOMIC | __GFP_NOWARN;
page_mask = GFP_ATOMIC | __GFP_COMP | __GFP_NOWARN;
for (order = 0, a_size = PAGE_SIZE; a_size < rqSz;
order++, a_size <<= 1) ;