From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 30 May 2018 09:35:39 -0400 From: Brian Foster To: Christoph Hellwig Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 03/18] xfs: simplify xfs_bmap_punch_delalloc_range Message-ID: <20180530133538.GC112411@bfoster.bfoster> References: <20180530100013.31358-1-hch@lst.de> <20180530100013.31358-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180530100013.31358-4-hch@lst.de> Sender: owner-linux-mm@kvack.org List-ID: On Wed, May 30, 2018 at 11:59:58AM +0200, Christoph Hellwig wrote: > Instead of using xfs_bmapi_read to find delalloc extents and then punch > them out using xfs_bunmapi, opencode the loop to iterate over the extents > and call xfs_bmap_del_extent_delay directly. This both simplifies the > code and reduces the number of extent tree lookups required. > > Signed-off-by: Christoph Hellwig > --- > fs/xfs/xfs_bmap_util.c | 84 ++++++++++++++---------------------------- > 1 file changed, 28 insertions(+), 56 deletions(-) > > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c > index 06badcbadeb4..f2b87873612d 100644 > --- a/fs/xfs/xfs_bmap_util.c > +++ b/fs/xfs/xfs_bmap_util.c > @@ -695,12 +695,10 @@ xfs_getbmap( > } > > /* > - * dead simple method of punching delalyed allocation blocks from a range in > - * the inode. Walks a block at a time so will be slow, but is only executed in > - * rare error cases so the overhead is not critical. This will always punch out > - * both the start and end blocks, even if the ranges only partially overlap > - * them, so it is up to the caller to ensure that partial blocks are not > - * passed in. > + * Dead simple method of punching delalyed allocation blocks from a range in > + * the inode. This will always punch out both the start and end blocks, even > + * if the ranges only partially overlap them, so it is up to the caller to > + * ensure that partial blocks are not passed in. > */ > int > xfs_bmap_punch_delalloc_range( > @@ -708,63 +706,37 @@ xfs_bmap_punch_delalloc_range( > xfs_fileoff_t start_fsb, > xfs_fileoff_t length) > { ... > + if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got)) > + return 0; > > - /* > - * Note: while we initialise the firstblock/dfops pair, they > - * should never be used because blocks should never be > - * allocated or freed for a delalloc extent and hence we need > - * don't cancel or finish them after the xfs_bunmapi() call. > - */ > - xfs_defer_init(&dfops, &firstblock); > - error = xfs_bunmapi(NULL, ip, start_fsb, 1, 0, 1, &firstblock, > - &dfops, &done); > - if (error) > - break; > + while (got.br_startoff + got.br_blockcount > start_fsb) { > + del = got; > + xfs_trim_extent(&del, start_fsb, length); > > - ASSERT(!xfs_defer_has_unfinished_work(&dfops)); > -next_block: > - start_fsb++; > - remaining--; > - } while(remaining > 0); > + if (del.br_blockcount && isnullstartblock(del.br_startblock)) { I think there's subtle behavior here that warrants a comment (and describes the somewhat funky logic). E.g., something like: /* * got might point to the extent after del in some cases. The next * iteration will detect this and step back to the previous extent. */ Alternatively, I find separating the if/else a bit more readable (see the appended hunk). But otherwise looks fine: Reviewed-by: Brian Foster > + error = xfs_bmap_del_extent_delay(ip, XFS_DATA_FORK, > + &icur, &got, &del); > + if (error || !xfs_iext_get_extent(ifp, &icur, &got)) > + break; > + } else { > + if (!xfs_iext_prev_extent(ifp, &icur, &got)) > + break; > + } > + } > > return error; > } > -- > 2.17.0 --- 8< --- diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c index f2b87873612d..0070b877ed94 100644 --- a/fs/xfs/xfs_bmap_util.c +++ b/fs/xfs/xfs_bmap_util.c @@ -727,15 +727,22 @@ xfs_bmap_punch_delalloc_range( del = got; xfs_trim_extent(&del, start_fsb, length); - if (del.br_blockcount && isnullstartblock(del.br_startblock)) { - error = xfs_bmap_del_extent_delay(ip, XFS_DATA_FORK, - &icur, &got, &del); - if (error || !xfs_iext_get_extent(ifp, &icur, &got)) - break; - } else { + /* + * A delete can push the cursor forward. Step back to the + * previous extent on non-delalloc or extents outside the + * target range. + */ + if (!del.br_blockcount || + !isnullstartblock(del.br_startblock)) { if (!xfs_iext_prev_extent(ifp, &icur, &got)) break; + continue; } + + error = xfs_bmap_del_extent_delay(ip, XFS_DATA_FORK, &icur, + &got, &del); + if (error || !xfs_iext_get_extent(ifp, &icur, &got)) + break; } return error;