Messages in this thread | | | Date | Tue, 27 Jun 2006 10:22:40 +0200 | From | Ingo Molnar <> | Subject | Re: GFS2 and DLM |
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* Nathan Scott <nathans@sgi.com> wrote:
> > */ > > buf = (xfs_caddr_t) kmem_zalloc(NBPP, KM_SLEEP); > > [...] > > > > where kmem_zalloc() may fail!!! > > Not with the flags it was given.
yeah, you are right - sorry about that.
XFS instead loops infinitely:
void * kmem_alloc(size_t size, unsigned int __nocast flags) { int retries = 0; gfp_t lflags = kmem_flags_convert(flags); void *ptr;
do { if (size < MAX_SLAB_SIZE || retries > MAX_VMALLOCS) ptr = kmalloc(size, lflags); else ptr = __vmalloc(size, lflags, PAGE_KERNEL); if (ptr || (flags & (KM_MAYFAIL|KM_NOSLEEP))) return ptr; if (!(++retries % 100)) printk(KERN_ERR "XFS: possible memory allocation " "deadlock in %s (mode:0x%x)\n", __FUNCTION__, lflags); blk_congestion_wait(WRITE, HZ/50); } while (1); }
which is in essence an open-coded GFP_NOFAIL implementation. Here's what __GFP_NOFAIL does:
if (gfp_mask & __GFP_NOFAIL) { blk_congestion_wait(WRITE, HZ/50); goto nofail_alloc; }
and since XFS makes use of KM_SLEEP in 130+ callsites, that means it is in essence using GFP_NOFAIL massively!
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