On Mon, Apr 17, 2017 at 01:52:15PM -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>
> ---
> v2: avoid 64-bit division when calculating block reservation
> ---
> fs/xfs/libxfs/xfs_trans_space.h | 18 ++++++++++++------
> fs/xfs/xfs_bmap_item.c | 7 ++++++-
> fs/xfs/xfs_reflink.c | 12 ++++++++++--
> 3 files changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_trans_space.h b/fs/xfs/libxfs/xfs_trans_space.h
> index 7917f6e..04278cf 100644
> --- a/fs/xfs/libxfs/xfs_trans_space.h
> +++ b/fs/xfs/libxfs/xfs_trans_space.h
> @@ -23,6 +23,16 @@
> */
> #define XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp) \
> (((mp)->m_rmap_mxr[0]) - ((mp)->m_rmap_mnr[0]))
> +static inline unsigned int
> +XFS_RMAPADD_SPACE_RES(
> + struct xfs_mount *mp)
> +{
> + return xfs_sb_version_hasrmapbt(&mp->m_sb) ? mp->m_rmap_maxlevels : 0;
Is the feature bit check really necessary (isn't it kind of a problem if
we're making an rmap reservation without the feature enabled)?
> +}
> +#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))
> #define XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp) \
> (((mp)->m_alloc_mxr[0]) - ((mp)->m_alloc_mnr[0]))
> #define XFS_EXTENTADD_SPACE_RES(mp,w) (XFS_BM_MAXLEVELS(mp,w) - 1)
> @@ -31,12 +41,8 @@
> XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp)) * \
> XFS_EXTENTADD_SPACE_RES(mp,w))
> #define XFS_SWAP_RMAP_SPACE_RES(mp,b,w)\
> - (((b + XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp) - 1) / \
> - XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp)) * \
> - XFS_EXTENTADD_SPACE_RES(mp,w) + \
> - ((b + XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp) - 1) / \
> - XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp)) * \
> - (mp)->m_rmap_maxlevels)
> + (XFS_NEXTENTADD_SPACE_RES((mp), (b), (w)) + \
> + XFS_NRMAPADD_SPACE_RES((mp), (b), (w)))
> #define XFS_DAENTER_1B(mp,w) \
> ((w) == XFS_DATA_FORK ? (mp)->m_dir_geo->fsbcount : 1)
> #define XFS_DAENTER_DBS(mp,w) \
> diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
> index 9bf57c7..055ab8f 100644
> --- a/fs/xfs/xfs_bmap_item.c
> +++ b/fs/xfs/xfs_bmap_item.c
> @@ -34,6 +34,8 @@
> #include "xfs_bmap.h"
> #include "xfs_icache.h"
> #include "xfs_trace.h"
> +#include "xfs_bmap_btree.h"
> +#include "xfs_trans_space.h"
>
>
> kmem_zone_t *xfs_bui_zone;
> @@ -402,6 +404,7 @@ xfs_bui_recover(
> struct xfs_inode *ip = NULL;
> struct xfs_defer_ops dfops;
> xfs_fsblock_t firstfsb;
> + unsigned int resblks;
>
> ASSERT(!test_bit(XFS_BUI_RECOVERED, &buip->bui_flags));
>
> @@ -446,7 +449,9 @@ xfs_bui_recover(
> return -EIO;
> }
>
> - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
> + resblks = XFS_SWAP_RMAP_SPACE_RES(mp, 1, XFS_DATA_FORK);
> + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, resblks, 0,
> + 0, &tp);
> 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..9b159f8 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.
> + */
> + WARN_ON(end_fsb - offset_fsb + 1 > ~0U);
> + resblks = min_t(xfs_fileoff_t, ~0U, end_fsb - offset_fsb + 1);
> + resblks = XFS_SWAP_RMAP_SPACE_RES(ip->i_mount, resblks,
> + XFS_DATA_FORK);
Perhaps use U32_MAX or UINT_MAX or something rather than ~0U? Also it
might be a good idea to point out in the comment that this is just to
avoid 64-bit division.
Otherwise this seems reasonable to me, but I can't help to wonder...
from a bigger picture standpoint, should we have already made these kind
of block reservations before we get to I/O completion processing?
Brian
> error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
> resblks, 0, 0, &tp);
> if (error)
> --
> 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
--
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
