On Mon, Apr 24, 2017 at 06:58:37PM -0700, Darrick J. Wong wrote: > In xfs_reflink_end_cow, we erroneously reserve only enough blocks to > handle adding 1 extent. This is problematic if we fragment free space, > have to do CoW, and then have to perform multiple bmap btree expansions. > Furthermore, the BUI recovery routine doesn't reserve /any/ blocks to > handle btree splits, so log recovery fails after our first error causes > the filesystem to go down. > > Therefore, refactor the transaction block reservation macros until we > have a macro that works for our deferred (re)mapping activities, and fix > both problems by using that macro. > > With 1k blocks we can hit this fairly often in g/187 if the scratch fs > is big enough. > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > --- > v3: don't use the swap-extents-with-rmap block reservation for cow > remapping; we should already have sufficient per-ag reservation > v2: avoid 64-bit division when calculating block reservation > --- > fs/xfs/libxfs/xfs_trans_space.h | 13 +++++++------ > fs/xfs/xfs_bmap_item.c | 7 ++++++- > fs/xfs/xfs_reflink.c | 12 ++++++++++-- > 3 files changed, 23 insertions(+), 9 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_trans_space.h b/fs/xfs/libxfs/xfs_trans_space.h > index 7917f6e..0044e14 100644 > --- a/fs/xfs/libxfs/xfs_trans_space.h > +++ b/fs/xfs/libxfs/xfs_trans_space.h > @@ -23,6 +23,11 @@ > */ > #define XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp) \ > (((mp)->m_rmap_mxr[0]) - ((mp)->m_rmap_mnr[0])) > +#define XFS_RMAPADD_SPACE_RES(mp) ((mp)->m_rmap_maxlevels) > +#define XFS_NRMAPADD_SPACE_RES(mp,b,w)\ > + (((b + XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp) - 1) / \ > + XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp)) * \ > + XFS_RMAPADD_SPACE_RES(mp)) Comments, please! (I know the existing defintions don't have any, but that's bad enough to start with..) > xfs_fsblock_t firstfsb; > + unsigned int resblks; > > ASSERT(!test_bit(XFS_BUI_RECOVERED, &buip->bui_flags)); > > @@ -447,7 +450,9 @@ xfs_bui_recover( > return -EIO; > } > > - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp); > + resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK); > + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, resblks, 0, > + 0, &tp); Do we really need that resblks variable? > if (error) > return error; > budp = xfs_trans_get_bud(tp, buip); > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > index c0f3754..aab156a 100644 > --- a/fs/xfs/xfs_reflink.c > +++ b/fs/xfs/xfs_reflink.c > @@ -705,8 +705,16 @@ xfs_reflink_end_cow( > offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset); > end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count); > > - /* Start a rolling transaction to switch the mappings */ > - resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK); > + /* > + * Start a rolling transaction to switch the mappings. We're > + * unlikely ever to have to remap 16T worth of single-block > + * extents, so just cap the worst case extent count to 2^32-1. > + * Stick a warning in just in case, and avoid 64-bit division. > + */ > + WARN_ON(end_fsb - offset_fsb + 1 > UINT_MAX); > + resblks = min_t(xfs_fileoff_t, UINT_MAX, end_fsb - offset_fsb + 1); I don't like unlikely statements. What prevents us from doing so? I think the way Linux limits writes to 32-bits using MAX_RW_COUNT does, but then the language should be more assertive here. I think we should also shut down the fs here if the assert fails - otherwise we'll leave a partially converted region around. A BUILD_BUG_ON on MAX_RW_COUNT might also be useful to make the whole scheme even safer. -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
