Messages in this thread | | | Date | Mon, 03 May 2010 09:06:18 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH] fs: use kmalloc() to allocate fdmem if possible |
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On 05/03/2010 03:15 AM, Tetsuo Handa wrote: > Avi Kivity wrote: > >> On 05/02/2010 07:46 PM, Changli Gao wrote: >> >>> use kmalloc() to allocate fdmem if possible. >>> >>> vmalloc() is used as a fallback solution for fdmem allocation. Two members are >>> added into the hole of the structure fdtable to indicate if vmalloc() is used >>> or not. >>> >>> >>> diff --git a/fs/file.c b/fs/file.c >>> index 34bb7f7..f71dd85 100644 >>> --- a/fs/file.c >>> +++ b/fs/file.c >>> @@ -39,28 +39,34 @@ int sysctl_nr_open_max = 1024 * 1024; /* raised later */ >>> */ >>> static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list); >>> >>> -static inline void * alloc_fdmem(unsigned int size) >>> +static inline void *alloc_fdmem(unsigned int size, unsigned short *use_vmalloc) >>> { >>> - if (size<= PAGE_SIZE) >>> - return kmalloc(size, GFP_KERNEL); >>> - else >>> - return vmalloc(size); >>> + void *data; >>> + >>> + data = kmalloc(size, GFP_KERNEL); >>> + if (data != NULL) { >>> + *use_vmalloc = 0; >>> + return data; >>> + } >>> + *use_vmalloc = 1; >>> + >>> + return vmalloc(size); >>> } >>> >>> >> Perhaps vmalloc() should do this by itself? vfree() can examine the >> pointer and call kfree() if it isn't within the vmalloc address range. >> > You can use is_vmalloc_addr(). > > if (is_vmalloc_addr(p)) > vfree(p); > else > kfree(p); >
My point is, vmalloc() and vfree should do this, not their callers:
vmalloc(size): if (size <= PAGE_SIZE) return kmalloc(size, GFP_KERNEL); ...
vfree(p): if (!is_vmalloc_addr(p) { kfree(p); return; } ...
-- Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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