| Message ID | 20180710060528.4071-7-hch@lst.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Tue, Jul 10, 2018 at 08:05:28AM +0200, Christoph Hellwig wrote: > Used the per-fork sequence counter to avoid lookups in the writeback code > unless the COW fork actually changed. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > fs/xfs/xfs_aops.c | 28 +++++++++++++++++++++++----- > fs/xfs/xfs_iomap.c | 4 +++- > fs/xfs/xfs_iomap.h | 2 +- > 3 files changed, 27 insertions(+), 7 deletions(-) > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 814100d27343..495d5e74fd00 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -29,6 +29,7 @@ > struct xfs_writepage_ctx { > struct xfs_bmbt_irec imap; > unsigned int io_type; > + unsigned int cow_seq; > struct xfs_ioend *ioend; > }; > > @@ -310,6 +311,7 @@ xfs_map_blocks( > struct xfs_mount *mp = ip->i_mount; > ssize_t count = i_blocksize(inode); > xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset), end_fsb; > + xfs_fileoff_t cow_fsb = NULLFILEOFF; > struct xfs_bmbt_irec imap; > int whichfork = XFS_DATA_FORK; > struct xfs_iext_cursor icur; > @@ -333,12 +335,15 @@ xfs_map_blocks( > * COW fork blocks can overlap data fork blocks even if the blocks > * aren't shared. COW I/O always takes precedent, so we must always > * check for overlap on reflink inodes unless the mapping is already a > - * COW one. > + * COW one, or the COW fork hasn't changed from the last time we looked > + * at it. > */ > imap_valid = offset_fsb >= wpc->imap.br_startoff && > offset_fsb < wpc->imap.br_startoff + wpc->imap.br_blockcount; > if (imap_valid && > - (!xfs_inode_has_cow_data(ip) || wpc->io_type == XFS_IO_COW)) > + (!xfs_inode_has_cow_data(ip) || > + wpc->io_type == XFS_IO_COW || > + wpc->cow_seq == ip->i_cowfp->if_seq)) > return 0; > > if (XFS_FORCED_SHUTDOWN(mp)) > @@ -364,8 +369,10 @@ xfs_map_blocks( > * it directly instead of looking up anything in the data fork. > */ > if (xfs_inode_has_cow_data(ip) && > - xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap) && > - imap.br_startoff <= offset_fsb) { > + xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap)) > + cow_fsb = imap.br_startoff; > + if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) { > + wpc->cow_seq = ip->i_cowfp->if_seq; > xfs_iunlock(ip, XFS_ILOCK_SHARED); > /* > * Truncate can race with writeback since writeback doesn't > @@ -411,6 +418,14 @@ xfs_map_blocks( > imap.br_startblock = HOLESTARTBLOCK; > wpc->io_type = XFS_IO_HOLE; > } else { > + /* > + * Truncate to the next COW extent if there is one. We'll > + * need to treat the COW range separately. > + */ > + if (cow_fsb != NULLFILEOFF && > + cow_fsb < imap.br_startoff + imap.br_blockcount) > + imap.br_blockcount = cow_fsb - imap.br_startoff; Hmm, this troubles me slightly -- a short time ago you removed the "trim this data fork mapping to the first overlap with a cow fork mapping" (i.e. xfs_reflink_trim_irec_to_next_cow) behavior on the grounds that _writepage_map calls _map_blocks for every block in the page and so it was unnecessary. But this seems to put that back. Why is that? --D > + > if (isnullstartblock(imap.br_startblock)) { > /* got a delalloc extent */ > wpc->io_type = XFS_IO_DELALLOC; > @@ -427,9 +442,12 @@ xfs_map_blocks( > trace_xfs_map_blocks_found(ip, offset, count, wpc->io_type, &imap); > return 0; > allocate_blocks: > - error = xfs_iomap_write_allocate(ip, whichfork, offset, &imap); > + error = xfs_iomap_write_allocate(ip, whichfork, offset, &imap, > + &wpc->cow_seq); > if (error) > return error; > + ASSERT(whichfork == XFS_COW_FORK || cow_fsb == NULLFILEOFF || > + imap.br_startoff + imap.br_blockcount <= cow_fsb); > wpc->imap = imap; > trace_xfs_map_blocks_alloc(ip, offset, count, wpc->io_type, &imap); > return 0; > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c > index fb9746cc7338..a843766bf7c5 100644 > --- a/fs/xfs/xfs_iomap.c > +++ b/fs/xfs/xfs_iomap.c > @@ -660,7 +660,8 @@ xfs_iomap_write_allocate( > xfs_inode_t *ip, > int whichfork, > xfs_off_t offset, > - xfs_bmbt_irec_t *imap) > + xfs_bmbt_irec_t *imap, > + unsigned int *cow_seq) > { > xfs_mount_t *mp = ip->i_mount; > xfs_fileoff_t offset_fsb, last_block; > @@ -784,6 +785,7 @@ xfs_iomap_write_allocate( > if (error) > goto error0; > > + *cow_seq = XFS_IFORK_PTR(ip, whichfork)->if_seq; > xfs_iunlock(ip, XFS_ILOCK_EXCL); > } > > diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h > index 83474c9cede9..c6170548831b 100644 > --- a/fs/xfs/xfs_iomap.h > +++ b/fs/xfs/xfs_iomap.h > @@ -14,7 +14,7 @@ struct xfs_bmbt_irec; > int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t, > struct xfs_bmbt_irec *, int); > int xfs_iomap_write_allocate(struct xfs_inode *, int, xfs_off_t, > - struct xfs_bmbt_irec *); > + struct xfs_bmbt_irec *, unsigned int *); > int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool); > > void xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *, > -- > 2.18.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 11, 2018 at 10:15:51AM -0700, Darrick J. Wong wrote: > Hmm, this troubles me slightly -- a short time ago you removed the "trim > this data fork mapping to the first overlap with a cow fork mapping" > (i.e. xfs_reflink_trim_irec_to_next_cow) behavior on the grounds that > _writepage_map calls _map_blocks for every block in the page and so it > was unnecessary. But this seems to put that back. Why is that? Because back then map_blocks did a lookup in the COW fork everytime (unless we are already on a COW mapping), and this patch wants to only look it up when the COW fork actually changed, so the trim is required now. -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 11, 2018 at 07:20:32PM +0200, Christoph Hellwig wrote: > On Wed, Jul 11, 2018 at 10:15:51AM -0700, Darrick J. Wong wrote: > > Hmm, this troubles me slightly -- a short time ago you removed the "trim > > this data fork mapping to the first overlap with a cow fork mapping" > > (i.e. xfs_reflink_trim_irec_to_next_cow) behavior on the grounds that > > _writepage_map calls _map_blocks for every block in the page and so it > > was unnecessary. But this seems to put that back. Why is that? > > Because back then map_blocks did a lookup in the COW fork everytime > (unless we are already on a COW mapping), and this patch wants to > only look it up when the COW fork actually changed, so the trim is > required now. Ah, ok. Mind if I change the comment to: /* * Truncate to the next COW extent if there is one. This is the only * opportunity to do this because we can skip COW fork lookups for the * subsequent blocks in the mapping; however, the requirement to treat * the COW range separately remains. */ I also wonder why we don't need to do the same for holes, but I think the answer is that any dirty page with a cow fork mapping must also have a data fork mapping (even if it's merely a delalloc reservation) and so a hole will never overlap with a cow fork mapping. --D > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 11, 2018 at 10:31:52AM -0700, Darrick J. Wong wrote: > On Wed, Jul 11, 2018 at 07:20:32PM +0200, Christoph Hellwig wrote: > > On Wed, Jul 11, 2018 at 10:15:51AM -0700, Darrick J. Wong wrote: > > > Hmm, this troubles me slightly -- a short time ago you removed the "trim > > > this data fork mapping to the first overlap with a cow fork mapping" > > > (i.e. xfs_reflink_trim_irec_to_next_cow) behavior on the grounds that > > > _writepage_map calls _map_blocks for every block in the page and so it > > > was unnecessary. But this seems to put that back. Why is that? > > > > Because back then map_blocks did a lookup in the COW fork everytime > > (unless we are already on a COW mapping), and this patch wants to > > only look it up when the COW fork actually changed, so the trim is > > required now. > > Ah, ok. Mind if I change the comment to: > > /* > * Truncate to the next COW extent if there is one. This is the only > * opportunity to do this because we can skip COW fork lookups for the > * subsequent blocks in the mapping; however, the requirement to treat > * the COW range separately remains. > */ > > I also wonder why we don't need to do the same for holes, but I think > the answer is that any dirty page with a cow fork mapping must also have > a data fork mapping (even if it's merely a delalloc reservation) and so > a hole will never overlap with a cow fork mapping. I'll update the comment. I'll need to resend against the 4.19-merge tree anyway, and I also found a little buglet in this patch (it updates wpc->cow_seq for all allocations and not just COW ones, with that fixed we should do even less lookups) -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 814100d27343..495d5e74fd00 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -29,6 +29,7 @@ struct xfs_writepage_ctx { struct xfs_bmbt_irec imap; unsigned int io_type; + unsigned int cow_seq; struct xfs_ioend *ioend; }; @@ -310,6 +311,7 @@ xfs_map_blocks( struct xfs_mount *mp = ip->i_mount; ssize_t count = i_blocksize(inode); xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset), end_fsb; + xfs_fileoff_t cow_fsb = NULLFILEOFF; struct xfs_bmbt_irec imap; int whichfork = XFS_DATA_FORK; struct xfs_iext_cursor icur; @@ -333,12 +335,15 @@ xfs_map_blocks( * COW fork blocks can overlap data fork blocks even if the blocks * aren't shared. COW I/O always takes precedent, so we must always * check for overlap on reflink inodes unless the mapping is already a - * COW one. + * COW one, or the COW fork hasn't changed from the last time we looked + * at it. */ imap_valid = offset_fsb >= wpc->imap.br_startoff && offset_fsb < wpc->imap.br_startoff + wpc->imap.br_blockcount; if (imap_valid && - (!xfs_inode_has_cow_data(ip) || wpc->io_type == XFS_IO_COW)) + (!xfs_inode_has_cow_data(ip) || + wpc->io_type == XFS_IO_COW || + wpc->cow_seq == ip->i_cowfp->if_seq)) return 0; if (XFS_FORCED_SHUTDOWN(mp)) @@ -364,8 +369,10 @@ xfs_map_blocks( * it directly instead of looking up anything in the data fork. */ if (xfs_inode_has_cow_data(ip) && - xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap) && - imap.br_startoff <= offset_fsb) { + xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap)) + cow_fsb = imap.br_startoff; + if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) { + wpc->cow_seq = ip->i_cowfp->if_seq; xfs_iunlock(ip, XFS_ILOCK_SHARED); /* * Truncate can race with writeback since writeback doesn't @@ -411,6 +418,14 @@ xfs_map_blocks( imap.br_startblock = HOLESTARTBLOCK; wpc->io_type = XFS_IO_HOLE; } else { + /* + * Truncate to the next COW extent if there is one. We'll + * need to treat the COW range separately. + */ + if (cow_fsb != NULLFILEOFF && + cow_fsb < imap.br_startoff + imap.br_blockcount) + imap.br_blockcount = cow_fsb - imap.br_startoff; + if (isnullstartblock(imap.br_startblock)) { /* got a delalloc extent */ wpc->io_type = XFS_IO_DELALLOC; @@ -427,9 +442,12 @@ xfs_map_blocks( trace_xfs_map_blocks_found(ip, offset, count, wpc->io_type, &imap); return 0; allocate_blocks: - error = xfs_iomap_write_allocate(ip, whichfork, offset, &imap); + error = xfs_iomap_write_allocate(ip, whichfork, offset, &imap, + &wpc->cow_seq); if (error) return error; + ASSERT(whichfork == XFS_COW_FORK || cow_fsb == NULLFILEOFF || + imap.br_startoff + imap.br_blockcount <= cow_fsb); wpc->imap = imap; trace_xfs_map_blocks_alloc(ip, offset, count, wpc->io_type, &imap); return 0; diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index fb9746cc7338..a843766bf7c5 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -660,7 +660,8 @@ xfs_iomap_write_allocate( xfs_inode_t *ip, int whichfork, xfs_off_t offset, - xfs_bmbt_irec_t *imap) + xfs_bmbt_irec_t *imap, + unsigned int *cow_seq) { xfs_mount_t *mp = ip->i_mount; xfs_fileoff_t offset_fsb, last_block; @@ -784,6 +785,7 @@ xfs_iomap_write_allocate( if (error) goto error0; + *cow_seq = XFS_IFORK_PTR(ip, whichfork)->if_seq; xfs_iunlock(ip, XFS_ILOCK_EXCL); } diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h index 83474c9cede9..c6170548831b 100644 --- a/fs/xfs/xfs_iomap.h +++ b/fs/xfs/xfs_iomap.h @@ -14,7 +14,7 @@ struct xfs_bmbt_irec; int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t, struct xfs_bmbt_irec *, int); int xfs_iomap_write_allocate(struct xfs_inode *, int, xfs_off_t, - struct xfs_bmbt_irec *); + struct xfs_bmbt_irec *, unsigned int *); int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool); void xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *,
Used the per-fork sequence counter to avoid lookups in the writeback code unless the COW fork actually changed. Signed-off-by: Christoph Hellwig <hch@lst.de> --- fs/xfs/xfs_aops.c | 28 +++++++++++++++++++++++----- fs/xfs/xfs_iomap.c | 4 +++- fs/xfs/xfs_iomap.h | 2 +- 3 files changed, 27 insertions(+), 7 deletions(-)