Hi Chao, On Thu, Oct 22, 2015 at 07:24:01PM +0800, Chao Yu wrote: > Hi Jaegeuk, > > > -----Original Message----- > > From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx] > > Sent: Thursday, October 22, 2015 6:30 AM > > To: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx; > > linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx > > Subject: Re: [f2fs-dev] [PATCH] f2fs: refactor __find_rev_next_{zero}_bit > > > > On Wed, Oct 21, 2015 at 02:16:43PM -0700, Jaegeuk Kim wrote: > > > This patch refactors __find_rev_next_{zero}_bit which was disabled previously > > > due to bugs. > > Actually I didn't know the history here, could you please explain details > about the bugs? then I can do the review. When I disabled the existing function by: commit e19ef527aa32f057710ec842fe656bffc263b0bb Author: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> Date: Mon May 18 11:45:15 2015 -0700 f2fs: avoid buggy functions I found a mismatch of results between the existing __find_rev_next_bit and f2fs_test_bit work. I remember it happened on __find_rev_next_bit sometimes by xfstests which include trim_fs. (I didn't get an error from __find_rev_zero_bit though.) Since I have no time to investigate the bug in more detail at that time, I just disabled it. But, now I'm trying to refactor the flow to fix this. Thanks, > > Thanks, > > > > > > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> > > > --- > > > fs/f2fs/segment.c | 106 +++++++++++++++++++++++++----------------------------- > > > 1 file changed, 49 insertions(+), 57 deletions(-) > > > > > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > > > index f37c212..50afc93 100644 > > > --- a/fs/f2fs/segment.c > > > +++ b/fs/f2fs/segment.c > > > @@ -29,6 +29,21 @@ static struct kmem_cache *discard_entry_slab; > > > static struct kmem_cache *sit_entry_set_slab; > > > static struct kmem_cache *inmem_entry_slab; > > > > > > +static unsigned long __reverse_ulong(unsigned char *str) > > > +{ > > > + unsigned long tmp = 0; > > > + int shift = 24, idx = 0; > > > + > > > +#if BITS_PER_LONG == 64 > > > + shift = 56; > > > +#endif > > > + while (shift >= 0) { > > > + tmp |= (unsigned long)str[idx++] << shift; > > > + shift -= BITS_PER_BYTE; > > > + } > > > + return tmp; > > > +} > > > + > > > /* > > > * __reverse_ffs is copied from include/asm-generic/bitops/__ffs.h since > > > * MSB and LSB are reversed in a byte by f2fs_set_bit. > > > @@ -38,27 +53,31 @@ static inline unsigned long __reverse_ffs(unsigned long word) > > > int num = 0; > > > > > > #if BITS_PER_LONG == 64 > > > - if ((word & 0xffffffff) == 0) { > > > + if ((word & 0xffffffff00000000) == 0) > > > > I fixed the sparse warning by modifying: > > if ((word & 0xffffffff00000000UL) == 0) > > > > Thanks, > > > > > num += 32; > > > + else > > > word >>= 32; > > > - } > > > #endif > > > - if ((word & 0xffff) == 0) { > > > + if ((word & 0xffff0000) == 0) > > > num += 16; > > > + else > > > word >>= 16; > > > - } > > > - if ((word & 0xff) == 0) { > > > + > > > + if ((word & 0xff00) == 0) > > > num += 8; > > > + else > > > word >>= 8; > > > - } > > > + > > > if ((word & 0xf0) == 0) > > > num += 4; > > > else > > > word >>= 4; > > > + > > > if ((word & 0xc) == 0) > > > num += 2; > > > else > > > word >>= 2; > > > + > > > if ((word & 0x2) == 0) > > > num += 1; > > > return num; > > > @@ -68,26 +87,16 @@ static inline unsigned long __reverse_ffs(unsigned long word) > > > * __find_rev_next(_zero)_bit is copied from lib/find_next_bit.c because > > > * f2fs_set_bit makes MSB and LSB reversed in a byte. > > > * Example: > > > - * LSB <--> MSB > > > - * f2fs_set_bit(0, bitmap) => 0000 0001 > > > - * f2fs_set_bit(7, bitmap) => 1000 0000 > > > + * MSB <--> LSB > > > + * f2fs_set_bit(0, bitmap) => 1000 0000 > > > + * f2fs_set_bit(7, bitmap) => 0000 0001 > > > */ > > > static unsigned long __find_rev_next_bit(const unsigned long *addr, > > > unsigned long size, unsigned long offset) > > > { > > > - while (!f2fs_test_bit(offset, (unsigned char *)addr)) > > > - offset++; > > > - > > > - if (offset > size) > > > - offset = size; > > > - > > > - return offset; > > > -#if 0 > > > const unsigned long *p = addr + BIT_WORD(offset); > > > unsigned long result = offset & ~(BITS_PER_LONG - 1); > > > unsigned long tmp; > > > - unsigned long mask, submask; > > > - unsigned long quot, rest; > > > > > > if (offset >= size) > > > return size; > > > @@ -97,14 +106,9 @@ static unsigned long __find_rev_next_bit(const unsigned long *addr, > > > if (!offset) > > > goto aligned; > > > > > > - tmp = *(p++); > > > - quot = (offset >> 3) << 3; > > > - rest = offset & 0x7; > > > - mask = ~0UL << quot; > > > - submask = (unsigned char)(0xff << rest) >> rest; > > > - submask <<= quot; > > > - mask &= submask; > > > - tmp &= mask; > > > + tmp = __reverse_ulong((unsigned char *)p); > > > + tmp &= ~0UL >> offset; > > > + > > > if (size < BITS_PER_LONG) > > > goto found_first; > > > if (tmp) > > > @@ -112,42 +116,34 @@ static unsigned long __find_rev_next_bit(const unsigned long *addr, > > > > > > size -= BITS_PER_LONG; > > > result += BITS_PER_LONG; > > > + p++; > > > aligned: > > > while (size & ~(BITS_PER_LONG-1)) { > > > - tmp = *(p++); > > > + tmp = __reverse_ulong((unsigned char *)p); > > > if (tmp) > > > goto found_middle; > > > result += BITS_PER_LONG; > > > size -= BITS_PER_LONG; > > > + p++; > > > } > > > if (!size) > > > return result; > > > - tmp = *p; > > > + > > > + tmp = __reverse_ulong((unsigned char *)p); > > > found_first: > > > - tmp &= (~0UL >> (BITS_PER_LONG - size)); > > > - if (tmp == 0UL) /* Are any bits set? */ > > > + tmp &= (~0UL << (BITS_PER_LONG - size)); > > > + if (!tmp) /* Are any bits set? */ > > > return result + size; /* Nope. */ > > > found_middle: > > > return result + __reverse_ffs(tmp); > > > -#endif > > > } > > > > > > static unsigned long __find_rev_next_zero_bit(const unsigned long *addr, > > > unsigned long size, unsigned long offset) > > > { > > > - while (f2fs_test_bit(offset, (unsigned char *)addr)) > > > - offset++; > > > - > > > - if (offset > size) > > > - offset = size; > > > - > > > - return offset; > > > -#if 0 > > > const unsigned long *p = addr + BIT_WORD(offset); > > > unsigned long result = offset & ~(BITS_PER_LONG - 1); > > > unsigned long tmp; > > > - unsigned long mask, submask; > > > - unsigned long quot, rest; > > > > > > if (offset >= size) > > > return size; > > > @@ -157,40 +153,36 @@ static unsigned long __find_rev_next_zero_bit(const unsigned long *addr, > > > if (!offset) > > > goto aligned; > > > > > > - tmp = *(p++); > > > - quot = (offset >> 3) << 3; > > > - rest = offset & 0x7; > > > - mask = ~(~0UL << quot); > > > - submask = (unsigned char)~((unsigned char)(0xff << rest) >> rest); > > > - submask <<= quot; > > > - mask += submask; > > > - tmp |= mask; > > > + tmp = __reverse_ulong((unsigned char *)p); > > > + tmp |= ~((~0UL << offset) >> offset); > > > + > > > if (size < BITS_PER_LONG) > > > goto found_first; > > > - if (~tmp) > > > + if (tmp != ~0UL) > > > goto found_middle; > > > > > > size -= BITS_PER_LONG; > > > result += BITS_PER_LONG; > > > + p++; > > > aligned: > > > while (size & ~(BITS_PER_LONG - 1)) { > > > - tmp = *(p++); > > > - if (~tmp) > > > + tmp = __reverse_ulong((unsigned char *)p); > > > + if (tmp != ~0UL) > > > goto found_middle; > > > result += BITS_PER_LONG; > > > size -= BITS_PER_LONG; > > > + p++; > > > } > > > if (!size) > > > return result; > > > - tmp = *p; > > > > > > + tmp = __reverse_ulong((unsigned char *)p); > > > found_first: > > > - tmp |= ~0UL << size; > > > - if (tmp == ~0UL) /* Are any bits zero? */ > > > + tmp |= ~(~0UL << (BITS_PER_LONG - size)); > > > + if (tmp == ~0UL) /* Are any bits zero? */ > > > return result + size; /* Nope. */ > > > found_middle: > > > return result + __reverse_ffz(tmp); > > > -#endif > > > } > > > > > > void register_inmem_page(struct inode *inode, struct page *page) > > > -- > > > 2.1.1 > > > > ------------------------------------------------------------------------------ > > _______________________________________________ > > Linux-f2fs-devel mailing list > > Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
