| Message ID | 1525968625-40825-1-git-send-email-yehs1@lenovo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) No, you've made gfp_zone even more complex than it already is. If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. > static inline enum zone_type gfp_zone(gfp_t flags) > { > enum zone_type z; > - int bit = (__force int) (flags & GFP_ZONEMASK); > + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > + > + if (z > OPT_ZONE_HIGHMEM) > + z = OPT_ZONE_HIGHMEM + > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > - ((1 << GFP_ZONES_SHIFT) - 1); > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > + VM_BUG_ON(z > ZONE_MOVABLE); > return z; > }
> From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On Behalf Of Matthew > Wilcox > On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) > > No, you've made gfp_zone even more complex than it already is. > If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. > Dear Matthew, The reason why I don't use OPT_ZONE_HIGHMEM for __GFP_HIGHMEM directly is that, for x86_64 platform there is no CONFIG_HIGHMEM, so OPT_ZONE_HIGHMEM shall always be equal to ZONE_NORMAL. For gfp_zone it is impossible to distinguish the meaning of lowest 3 bits in flags. How can gfp_zone to understand it comes from OPT_ZONE_HIGHMEM or ZONE_NORMAL? And the most pained thing is that, if __GFP_HIGHMEM with movable flag enabled, it means that ZONE_MOVABLE shall be returned. That is different from ZONE_DMA, ZONE_DMA32 and ZONE_NORMAL. I was thinking... Whether it is possible to use other judgement condition to decide OPT_ZONE_HIGHMEM or ZONE_MOVABLE shall be returned from gfp_zone. Sincerely, Huaisheng Ye > > static inline enum zone_type gfp_zone(gfp_t flags) > > { > > enum zone_type z; > > - int bit = (__force int) (flags & GFP_ZONEMASK); > > + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > > + > > + if (z > OPT_ZONE_HIGHMEM) > > + z = OPT_ZONE_HIGHMEM + > > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > > > - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > > - ((1 << GFP_ZONES_SHIFT) - 1); > > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > > + VM_BUG_ON(z > ZONE_MOVABLE); > > return z; > > }
On Fri, May 11, 2018 at 03:24:34AM +0000, Huaisheng HS1 Ye wrote: > > From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On Behalf Of Matthew > > Wilcox > > On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > > > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > > > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > > > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > > > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > > > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > > > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) > > > > No, you've made gfp_zone even more complex than it already is. > > If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. > > > Dear Matthew, > > The reason why I don't use OPT_ZONE_HIGHMEM for __GFP_HIGHMEM directly is that, for x86_64 platform there is no CONFIG_HIGHMEM, so OPT_ZONE_HIGHMEM shall always be equal to ZONE_NORMAL. Right. On 64-bit platforms, if somebody asks for HIGHMEM, they should get NORMAL pages. > For gfp_zone it is impossible to distinguish the meaning of lowest 3 bits in flags. How can gfp_zone to understand it comes from OPT_ZONE_HIGHMEM or ZONE_NORMAL? > And the most pained thing is that, if __GFP_HIGHMEM with movable flag enabled, it means that ZONE_MOVABLE shall be returned. > That is different from ZONE_DMA, ZONE_DMA32 and ZONE_NORMAL. The point of this exercise is to actually encode the zone number in the bottom bits of the GFP flags instead of something which has to be interpreted into a zone number. When somebody sets __GFP_MOVABLE, they should also be setting ZONE_MOVABLE: -#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ +#define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) One thing that does need to change is: -#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE) +#define GFP_HIGHUSER_MOVABLE (GFP_USER | __GFP_MOVABLE) otherwise we'll be OR'ing ZONE_MOVABLE and ZONE_HIGHMEM together. > I was thinking... > Whether it is possible to use other judgement condition to decide OPT_ZONE_HIGHMEM or ZONE_MOVABLE shall be returned from gfp_zone. > > Sincerely, > Huaisheng Ye > > > > > static inline enum zone_type gfp_zone(gfp_t flags) > > > { > > > enum zone_type z; > > > - int bit = (__force int) (flags & GFP_ZONEMASK); > > > + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > > > + > > > + if (z > OPT_ZONE_HIGHMEM) > > > + z = OPT_ZONE_HIGHMEM + > > > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > > > > > - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > > > - ((1 << GFP_ZONES_SHIFT) - 1); > > > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > > > + VM_BUG_ON(z > ZONE_MOVABLE); > > > return z; > > > } >
> From: Matthew Wilcox [mailto:willy@infradead.org] > Sent: Friday, May 11, 2018 9:26 PM> > On Fri, May 11, 2018 at 03:24:34AM +0000, Huaisheng HS1 Ye wrote: > > > From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On Behalf Of > Matthew > > > Wilcox > > > On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > > > > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > > > > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > > > > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > > > > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > > > > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > > > > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) > > > > > > No, you've made gfp_zone even more complex than it already is. > > > If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. > > > > > Dear Matthew, > > > > The reason why I don't use OPT_ZONE_HIGHMEM for __GFP_HIGHMEM directly is that, > for x86_64 platform there is no CONFIG_HIGHMEM, so OPT_ZONE_HIGHMEM shall always be > equal to ZONE_NORMAL. > > Right. On 64-bit platforms, if somebody asks for HIGHMEM, they should > get NORMAL pages. > > > For gfp_zone it is impossible to distinguish the meaning of lowest 3 bits in flags. > How can gfp_zone to understand it comes from OPT_ZONE_HIGHMEM or ZONE_NORMAL? > > And the most pained thing is that, if __GFP_HIGHMEM with movable flag enabled, it > means that ZONE_MOVABLE shall be returned. > > That is different from ZONE_DMA, ZONE_DMA32 and ZONE_NORMAL. > > The point of this exercise is to actually encode the zone number in > the bottom bits of the GFP flags instead of something which has to be > interpreted into a zone number. When somebody sets __GFP_MOVABLE, they > should also be setting ZONE_MOVABLE: > > -#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ > +#define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) > I am afraid we couldn't do that, because __GFP_MOVABLE would be used potentially with other __GFPs like __GFP_DMA and __GFP_DMA32. Let's go back to the previous example. We assume ZONE_DMA equals to 0, and ZONE_DMA32 equals to 1. After encoding with ZONE_NORMAL (which equals to 2), we could get that. #define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) #define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) __GPF_DMA = 0b 0010 __GPF_DMA32 = 0b 0011 We assume ZONE_MOVABLE equals to 3, #define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) __GFP_MOVABLE = 0b 1001 If we OR'ing __GFP_MOVABLE and either __GFP_DMA or __GFP_DMA32, we could get same result as '0b 1011'. This is unacceptable, because inline function gfp_zone couldn't distinguish that is a request of ZONE_DMA or ZONE_DMA32 from parameter flags. Once more, I think if we want to encode ZONE_MOVABLE to __GFP_MOVABLE, then the operation of __GFP_MOVABLE OR'ing with any other __GFP* would have risk. Sincerely, Huaisheng Ye > One thing that does need to change is: > > -#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE) > +#define GFP_HIGHUSER_MOVABLE (GFP_USER | __GFP_MOVABLE) > > otherwise we'll be OR'ing ZONE_MOVABLE and ZONE_HIGHMEM together. > > > I was thinking... > > Whether it is possible to use other judgement condition to decide OPT_ZONE_HIGHMEM > or ZONE_MOVABLE shall be returned from gfp_zone. > > > > Sincerely, > > Huaisheng Ye > > > > > > > > static inline enum zone_type gfp_zone(gfp_t flags) > > > > { > > > > enum zone_type z; > > > > - int bit = (__force int) (flags & GFP_ZONEMASK); > > > > + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > > > > + > > > > + if (z > OPT_ZONE_HIGHMEM) > > > > + z = OPT_ZONE_HIGHMEM + > > > > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > > > > > > > - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > > > > - ((1 << GFP_ZONES_SHIFT) - 1); > > > > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > > > > + VM_BUG_ON(z > ZONE_MOVABLE); > > > > return z; > > > > } > >
On Sat, May 12, 2018 at 11:35:00AM +0000, Huaisheng HS1 Ye wrote: > > The point of this exercise is to actually encode the zone number in > > the bottom bits of the GFP flags instead of something which has to be > > interpreted into a zone number. When somebody sets __GFP_MOVABLE, they > > should also be setting ZONE_MOVABLE: > > > > -#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ > > +#define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) > > > I am afraid we couldn't do that, because __GFP_MOVABLE would be used potentially with other __GFPs like __GFP_DMA and __GFP_DMA32. That's not a combination that makes much sense. I know it's permitted today (and it has the effect of being a no-op), but when you think about it, it doesn't actually make any sense.
> From: Matthew Wilcox [mailto:willy@infradead.org] > Sent: Saturday, May 12, 2018 10:23 PM> > On Sat, May 12, 2018 at 11:35:00AM +0000, Huaisheng HS1 Ye wrote: > > > The point of this exercise is to actually encode the zone number in > > > the bottom bits of the GFP flags instead of something which has to be > > > interpreted into a zone number. When somebody sets __GFP_MOVABLE, they > > > should also be setting ZONE_MOVABLE: > > > > > > -#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed > */ > > > +#define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ > ZONE_NORMAL))) > > > > > I am afraid we couldn't do that, because __GFP_MOVABLE would be used potentially > with other __GFPs like __GFP_DMA and __GFP_DMA32. > > That's not a combination that makes much sense. I know it's permitted today > (and it has the effect of being a no-op), but when you think about it, it > doesn't actually make any sense. Yes, you are right. After checking almost all references of __GFP_MOVABLE and other __GFP_* flags, perhaps I was far to get excessive pursuit of logical correctness. For those nonsense combinations, I should ignore them. Current GFP_ZONE_TABLE can ensure all logical correctness. That makes me want to pursue same effect. Next, I will revise the patch according to your advice, then try to get overall testing result as far as possible. There are many combinations because of a lot of conditions in file system and drivers. Hope I could test all things related to the lower 4 bits of gfp. Sincerely, Huaisheng Ye
> From: Matthew Wilcox [mailto:willy@infradead.org] > Sent: Friday, May 11, 2018 9:26 PM > On Fri, May 11, 2018 at 03:24:34AM +0000, Huaisheng HS1 Ye wrote: > > > From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On Behalf Of > Matthew > > > Wilcox > > > On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > > > > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > > > > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > > > > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > > > > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > > > > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > > > > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) > > > > > > No, you've made gfp_zone even more complex than it already is. > > > If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. > > > > > Dear Matthew, > > > > The reason why I don't use OPT_ZONE_HIGHMEM for __GFP_HIGHMEM directly is that, > for x86_64 platform there is no CONFIG_HIGHMEM, so OPT_ZONE_HIGHMEM shall always be > equal to ZONE_NORMAL. > > Right. On 64-bit platforms, if somebody asks for HIGHMEM, they should > get NORMAL pages. > > > For gfp_zone it is impossible to distinguish the meaning of lowest 3 bits in flags. > How can gfp_zone to understand it comes from OPT_ZONE_HIGHMEM or ZONE_NORMAL? > > And the most pained thing is that, if __GFP_HIGHMEM with movable flag enabled, it > means that ZONE_MOVABLE shall be returned. > > That is different from ZONE_DMA, ZONE_DMA32 and ZONE_NORMAL. > > The point of this exercise is to actually encode the zone number in > the bottom bits of the GFP flags instead of something which has to be > interpreted into a zone number. When somebody sets __GFP_MOVABLE, they > should also be setting ZONE_MOVABLE: > > -#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ > +#define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) > > One thing that does need to change is: > > -#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE) > +#define GFP_HIGHUSER_MOVABLE (GFP_USER | __GFP_MOVABLE) > > otherwise we'll be OR'ing ZONE_MOVABLE and ZONE_HIGHMEM together. Dear Matthew, After thinking it over and over, I am afraid there is something needs to be discussed here. You know current X86_64 config file of kernel doesn't enable CONFIG_HIGHMEM, that is to say from this below, #define __GFP_HIGHMEM ((__force gfp_t)OPT_ZONE_HIGHMEM ^ ZONE_NORMAL) __GFP_HIGHMEM should equal to 0b0000, same as the value of ZONE_NORMAL gets encoded. If we define __GFP_MOVABLE like this, #define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) Just like your introduced before, with this modification when somebody sets __GFP_MOVABLE, they should also be setting ZONE_MOVABLE. That brings us a problem, current mm (GFP_ZONE_TABLE) treats __GFP_MOVABLE as ZONE_NORMAL with movable policy, if without __GFP_HIGHMEM. The mm shall allocate a page or pages from migrate movable list of ZONE_NORMAL's freelist. So that conflicts with this modification. And I have checked current kernel, some of function directly set parameter gfp like this. For example, in fs/ext4/extents.c __read_extent_tree_block, bh = sb_getblk_gfp(inode->i_sb, pblk, __GFP_MOVABLE | GFP_NOFS); for these situations, I think only modify GFP_HIGHUSER_MOVABLE is not enough. I am preparing a workaround to solve this in the V2 patch. Later I will upload it to email loop. Sincerely, Huaisheng Ye > > I was thinking... > > Whether it is possible to use other judgement condition to decide OPT_ZONE_HIGHMEM > or ZONE_MOVABLE shall be returned from gfp_zone. > > > > Sincerely, > > Huaisheng Ye > > > > > > > > static inline enum zone_type gfp_zone(gfp_t flags) > > > > { > > > > enum zone_type z; > > > > - int bit = (__force int) (flags & GFP_ZONEMASK); > > > > + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > > > > + > > > > + if (z > OPT_ZONE_HIGHMEM) > > > > + z = OPT_ZONE_HIGHMEM + > > > > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > > > > > > > - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > > > > - ((1 << GFP_ZONES_SHIFT) - 1); > > > > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > > > > + VM_BUG_ON(z > ZONE_MOVABLE); > > > > return z; > > > > } > >
diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 1a4582b..578cef7 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -16,9 +16,7 @@ */ /* Plain integer GFP bitmasks. Do not use this directly. */ -#define ___GFP_DMA 0x01u -#define ___GFP_HIGHMEM 0x02u -#define ___GFP_DMA32 0x04u +#define ___GFP_ZONE_MASK 0x07u #define ___GFP_MOVABLE 0x08u #define ___GFP_RECLAIMABLE 0x10u #define ___GFP_HIGH 0x20u @@ -53,11 +51,11 @@ * without the underscores and use them consistently. The definitions here may * be used in bit comparisons. */ -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) #define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ -#define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE) +#define GFP_ZONEMASK ((__force gfp_t)___GFP_ZONE_MASK | ___GFP_MOVABLE) /* * Page mobility and placement hints @@ -326,86 +324,16 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags) #define OPT_ZONE_DMA32 ZONE_NORMAL #endif -/* - * GFP_ZONE_TABLE is a word size bitstring that is used for looking up the - * zone to use given the lowest 4 bits of gfp_t. Entries are GFP_ZONES_SHIFT - * bits long and there are 16 of them to cover all possible combinations of - * __GFP_DMA, __GFP_DMA32, __GFP_MOVABLE and __GFP_HIGHMEM. - * - * The zone fallback order is MOVABLE=>HIGHMEM=>NORMAL=>DMA32=>DMA. - * But GFP_MOVABLE is not only a zone specifier but also an allocation - * policy. Therefore __GFP_MOVABLE plus another zone selector is valid. - * Only 1 bit of the lowest 3 bits (DMA,DMA32,HIGHMEM) can be set to "1". - * - * bit result - * ================= - * 0x0 => NORMAL - * 0x1 => DMA or NORMAL - * 0x2 => HIGHMEM or NORMAL - * 0x3 => BAD (DMA+HIGHMEM) - * 0x4 => DMA32 or DMA or NORMAL - * 0x5 => BAD (DMA+DMA32) - * 0x6 => BAD (HIGHMEM+DMA32) - * 0x7 => BAD (HIGHMEM+DMA32+DMA) - * 0x8 => NORMAL (MOVABLE+0) - * 0x9 => DMA or NORMAL (MOVABLE+DMA) - * 0xa => MOVABLE (Movable is valid only if HIGHMEM is set too) - * 0xb => BAD (MOVABLE+HIGHMEM+DMA) - * 0xc => DMA32 (MOVABLE+DMA32) - * 0xd => BAD (MOVABLE+DMA32+DMA) - * 0xe => BAD (MOVABLE+DMA32+HIGHMEM) - * 0xf => BAD (MOVABLE+DMA32+HIGHMEM+DMA) - * - * GFP_ZONES_SHIFT must be <= 2 on 32 bit platforms. - */ - -#if defined(CONFIG_ZONE_DEVICE) && (MAX_NR_ZONES-1) <= 4 -/* ZONE_DEVICE is not a valid GFP zone specifier */ -#define GFP_ZONES_SHIFT 2 -#else -#define GFP_ZONES_SHIFT ZONES_SHIFT -#endif - -#if 16 * GFP_ZONES_SHIFT > BITS_PER_LONG -#error GFP_ZONES_SHIFT too large to create GFP_ZONE_TABLE integer -#endif - -#define GFP_ZONE_TABLE ( \ - (ZONE_NORMAL << 0 * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_DMA << ___GFP_DMA * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_DMA32 << ___GFP_DMA32 * GFP_ZONES_SHIFT) \ - | (ZONE_NORMAL << ___GFP_MOVABLE * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * GFP_ZONES_SHIFT) \ - | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * GFP_ZONES_SHIFT)\ - | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * GFP_ZONES_SHIFT)\ -) - -/* - * GFP_ZONE_BAD is a bitmap for all combinations of __GFP_DMA, __GFP_DMA32 - * __GFP_HIGHMEM and __GFP_MOVABLE that are not permitted. One flag per - * entry starting with bit 0. Bit is set if the combination is not - * allowed. - */ -#define GFP_ZONE_BAD ( \ - 1 << (___GFP_DMA | ___GFP_HIGHMEM) \ - | 1 << (___GFP_DMA | ___GFP_DMA32) \ - | 1 << (___GFP_DMA32 | ___GFP_HIGHMEM) \ - | 1 << (___GFP_DMA | ___GFP_DMA32 | ___GFP_HIGHMEM) \ - | 1 << (___GFP_MOVABLE | ___GFP_HIGHMEM | ___GFP_DMA) \ - | 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_DMA) \ - | 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_HIGHMEM) \ - | 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_DMA | ___GFP_HIGHMEM) \ -) - static inline enum zone_type gfp_zone(gfp_t flags) { enum zone_type z; - int bit = (__force int) (flags & GFP_ZONEMASK); + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; + + if (z > OPT_ZONE_HIGHMEM) + z = OPT_ZONE_HIGHMEM + + !!((__force unsigned int)flags & ___GFP_MOVABLE); - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & - ((1 << GFP_ZONES_SHIFT) - 1); - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); + VM_BUG_ON(z > ZONE_MOVABLE); return z; }
Replace GFP_ZONE_TABLE and GFP_ZONE_BAD with encoded zone number. Delete ___GFP_DMA, ___GFP_HIGHMEM and ___GFP_DMA32 from GFP bitmasks, the bottom three bits of GFP mask is reserved for storing encoded zone number. The encoding method is XOR. Get zone number from enum zone_type, then encode the number with ZONE_NORMAL by XOR operation. The goal is to make sure ZONE_NORMAL can be encoded to zero. So, the compatibility can be guaranteed, such as GFP_KERNEL and GFP_ATOMIC can be used as before. Reserve __GFP_MOVABLE in bit 3, so that it can continue to be used as a flag. Same as before, __GFP_MOVABLE respresents movable migrate type for ZONE_DMA, ZONE_DMA32, and ZONE_NORMAL. But when it is enabled with __GFP_HIGHMEM, ZONE_MOVABLE shall be returned instead of ZONE_HIGHMEM. Decode zone number within gfp_zone, firstly decode its number with bottom three bits of flags. Then, return correct zone_type according to flag movable if zone type is larger than OPT_ZONE_HIGHMEM. The theory of encoding and decoding is, A ^ B ^ B = A Suggested-by: Matthew Wilcox <willy@infradead.org> Signed-off-by: Huaisheng Ye <yehs1@lenovo.com> --- include/linux/gfp.h | 94 +++++++---------------------------------------------- 1 file changed, 11 insertions(+), 83 deletions(-)