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Wong" Cc: linux-xfs@vger.kernel.org, david@fromorbit.com, hch@infradead.org, allison.henderson@oracle.com Subject: Re: [PATCH V8 12/14] xfs: Compute bmap extent alignments in a separate function Date: Fri, 30 Oct 2020 21:56:57 +0530 Message-ID: <802040417.dp7cjt2klD@garuda> In-Reply-To: <20201030155212.GQ1061252@magnolia> References: <20201029101348.4442-1-chandanrlinux@gmail.com> <2167513.2nQQj6O1E8@garuda> <20201030155212.GQ1061252@magnolia> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Friday 30 October 2020 9:22:12 PM IST Darrick J. Wong wrote: > On Fri, Oct 30, 2020 at 01:46:18PM +0530, Chandan Babu R wrote: > > On Friday 30 October 2020 3:51:30 AM IST Darrick J. Wong wrote: > > > On Thu, Oct 29, 2020 at 03:43:46PM +0530, Chandan Babu R wrote: > > > > This commit moves over the code which computes stripe alignment and > > > > extent size hint alignment into a separate function. Apart from > > > > xfs_bmap_btalloc(), the new function will be used by another function > > > > introduced in a future commit. > > > > > > > > Reviewed-by: Allison Henderson > > > > Signed-off-by: Chandan Babu R > > > > --- > > > > fs/xfs/libxfs/xfs_bmap.c | 88 +++++++++++++++++++++++----------------- > > > > 1 file changed, 51 insertions(+), 37 deletions(-) > > > > > > > > diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c > > > > index 64c4d0e384a5..935f2d506748 100644 > > > > --- a/fs/xfs/libxfs/xfs_bmap.c > > > > +++ b/fs/xfs/libxfs/xfs_bmap.c > > > > @@ -3463,13 +3463,58 @@ xfs_bmap_btalloc_accounting( > > > > args->len); > > > > } > > > > > > > > +static void > > > > > > Why not return stripe_align instead of passing pointers? > > > > xfs_bmap_exact_minlen_extent_alloc() introduced in the last patch would invoke > > this function passing NULL value as the third argument i.e. it does not need > > "stripe alignment" to be computed. Hence xfs_bmap_exact_minlen_extent_alloc() > > would ignore the return value of xfs_bmap_compute_alignments(). This was the > > reason for deciding on passing a pointer to the stripe_align variable as an > > argument. > > I would have thought that an out parameter that isn't used by all > callers would be the perfect use of a return, especially since passing > by pointer means that the compiler has to spill stripe_align to a memory > location both here and in the callers and cannot keep the value in > registers. You are right. I will implement the change pointed out by you. Thanks once again for your suggestions. > > --D > > > > > > > > +xfs_bmap_compute_alignments( > > > > + struct xfs_bmalloca *ap, > > > > + struct xfs_alloc_arg *args, > > > > + int *stripe_align) > > > > +{ > > > > + struct xfs_mount *mp = args->mp; > > > > + xfs_extlen_t align = 0; /* minimum allocation alignment */ > > > > + int error; > > > > + > > > > + /* stripe alignment for allocation is determined by mount parameters */ > > > > + *stripe_align = 0; > > > > + if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC)) > > > > + *stripe_align = mp->m_swidth; > > > > + else if (mp->m_dalign) > > > > + *stripe_align = mp->m_dalign; > > > > + > > > > + if (ap->flags & XFS_BMAPI_COWFORK) > > > > + align = xfs_get_cowextsz_hint(ap->ip); > > > > + else if (ap->datatype & XFS_ALLOC_USERDATA) > > > > + align = xfs_get_extsz_hint(ap->ip); > > > > + if (align) { > > > > + error = xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, > > > > + align, 0, ap->eof, 0, ap->conv, > > > > + &ap->offset, &ap->length); > > > > + ASSERT(!error); > > > > + ASSERT(ap->length); > > > > + } > > > > + > > > > + /* apply extent size hints if obtained earlier */ > > > > + if (align) { > > > > + args->prod = align; > > > > + div_u64_rem(ap->offset, args->prod, &args->mod); > > > > + if (args->mod) > > > > + args->mod = args->prod - args->mod; > > > > + } else if (mp->m_sb.sb_blocksize >= PAGE_SIZE) { > > > > + args->prod = 1; > > > > + args->mod = 0; > > > > + } else { > > > > + args->prod = PAGE_SIZE >> mp->m_sb.sb_blocklog; > > > > + div_u64_rem(ap->offset, args->prod, &args->mod); > > > > + if (args->mod) > > > > + args->mod = args->prod - args->mod; > > > > + } > > > > +} > > > > + > > > > STATIC int > > > > xfs_bmap_btalloc( > > > > struct xfs_bmalloca *ap) /* bmap alloc argument struct */ > > > > { > > > > xfs_mount_t *mp; /* mount point structure */ > > > > xfs_alloctype_t atype = 0; /* type for allocation routines */ > > > > - xfs_extlen_t align = 0; /* minimum allocation alignment */ > > > > xfs_agnumber_t fb_agno; /* ag number of ap->firstblock */ > > > > xfs_agnumber_t ag; > > > > xfs_alloc_arg_t args; > > > > @@ -3489,25 +3534,11 @@ xfs_bmap_btalloc( > > > > > > > > mp = ap->ip->i_mount; > > > > > > > > - /* stripe alignment for allocation is determined by mount parameters */ > > > > - stripe_align = 0; > > > > - if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC)) > > > > - stripe_align = mp->m_swidth; > > > > - else if (mp->m_dalign) > > > > - stripe_align = mp->m_dalign; > > > > - > > > > - if (ap->flags & XFS_BMAPI_COWFORK) > > > > - align = xfs_get_cowextsz_hint(ap->ip); > > > > - else if (ap->datatype & XFS_ALLOC_USERDATA) > > > > - align = xfs_get_extsz_hint(ap->ip); > > > > - if (align) { > > > > - error = xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, > > > > - align, 0, ap->eof, 0, ap->conv, > > > > - &ap->offset, &ap->length); > > > > - ASSERT(!error); > > > > - ASSERT(ap->length); > > > > - } > > > > + memset(&args, 0, sizeof(args)); > > > > + args.tp = ap->tp; > > > > + args.mp = mp; > > > > > > FWIW you might as well clean up the variable declarations while you're > > > moving this stuff around: > > > > > > STATIC int > > > xfs_bmap_btalloc( > > > struct xfs_bmalloca *ap) > > > { > > > struct xfs_mount *mp = ap->ip->i_mount; > > > struct xfs_alloc_arg args = { .tp = ap->tp, .mp = mp }; > > > > > > And then you can get rid of the memset call. > > > > Sure, I will make the changes that have been suggested. > > > > > > > > AFAICT there aren't any data dependencies between the parts where we > > > initialize args.fsbno and where we set args.prod and args.mod, so I > > > guess this is a reasonable hoist. > > > > > > Other than those cleanups, this looks ok to me. > > > > > > --D > > > > > > > > > > > + xfs_bmap_compute_alignments(ap, &args, &stripe_align); > > > > > > > > nullfb = ap->tp->t_firstblock == NULLFSBLOCK; > > > > fb_agno = nullfb ? NULLAGNUMBER : XFS_FSB_TO_AGNO(mp, > > > > @@ -3538,9 +3569,6 @@ xfs_bmap_btalloc( > > > > * Normal allocation, done through xfs_alloc_vextent. > > > > */ > > > > tryagain = isaligned = 0; > > > > - memset(&args, 0, sizeof(args)); > > > > - args.tp = ap->tp; > > > > - args.mp = mp; > > > > args.fsbno = ap->blkno; > > > > args.oinfo = XFS_RMAP_OINFO_SKIP_UPDATE; > > > > > > > > @@ -3571,21 +3599,7 @@ xfs_bmap_btalloc( > > > > args.total = ap->total; > > > > args.minlen = ap->minlen; > > > > } > > > > - /* apply extent size hints if obtained earlier */ > > > > - if (align) { > > > > - args.prod = align; > > > > - div_u64_rem(ap->offset, args.prod, &args.mod); > > > > - if (args.mod) > > > > - args.mod = args.prod - args.mod; > > > > - } else if (mp->m_sb.sb_blocksize >= PAGE_SIZE) { > > > > - args.prod = 1; > > > > - args.mod = 0; > > > > - } else { > > > > - args.prod = PAGE_SIZE >> mp->m_sb.sb_blocklog; > > > > - div_u64_rem(ap->offset, args.prod, &args.mod); > > > > - if (args.mod) > > > > - args.mod = args.prod - args.mod; > > > > - } > > > > + > > > > /* > > > > * If we are not low on available data blocks, and the underlying > > > > * logical volume manager is a stripe, and the file offset is zero then > > > > > > > > -- chandan