On Mon, Dec 03, 2018 at 05:25:02PM -0500, Christoph Hellwig wrote:
> If we have racing buffered and direct I/O COW fork extents under
> writeback can have been moved to the data fork by the time we call
> xfs_reflink_convert_cow from xfs_submit_ioend. This would be mostly
> harmless as the block numbers don't change by this move, except for
> the fact that xfs_bmapi_write will crash or trigger asserts when
> not finding existing extents, even despite trying to paper over this
> with the XFS_BMAPI_CONVERT_ONLY flag.
>
> Instead of special casing non-transaction conversions in the already
> way too complicated xfs_bmapi_write just add a new helper for the much
> simpler non-transactional COW fork case, which simplify ignores not
> found extents.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/libxfs/xfs_bmap.c | 12 ++------
> fs/xfs/libxfs/xfs_bmap.h | 8 +++---
> fs/xfs/xfs_reflink.c | 61 +++++++++++++++++++++++++---------------
> 3 files changed, 45 insertions(+), 36 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 1992ed8a60b0..fbed7ed34a7f 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -2029,7 +2029,7 @@ xfs_bmap_add_extent_delay_real(
> /*
> * Convert an unwritten allocation to a real allocation or vice versa.
> */
> -STATIC int /* error */
> +int /* error */
> xfs_bmap_add_extent_unwritten_real(
> struct xfs_trans *tp,
> xfs_inode_t *ip, /* incore inode pointer */
> @@ -4236,9 +4236,7 @@ xfs_bmapi_write(
>
> ASSERT(*nmap >= 1);
> ASSERT(*nmap <= XFS_BMAP_MAX_NMAP);
> - ASSERT(tp != NULL ||
> - (flags & (XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK)) ==
> - (XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK));
> + ASSERT(tp != NULL);
> ASSERT(len > 0);
> ASSERT(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_LOCAL);
> ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
> @@ -4316,9 +4314,6 @@ xfs_bmapi_write(
> * locked and hence a truncate will block on them
> * first.
> */
> - ASSERT(!((flags & XFS_BMAPI_CONVERT) &&
> - (flags & XFS_BMAPI_COWFORK)));
> -
> if (flags & XFS_BMAPI_DELALLOC) {
> if (eof || bno >= end)
> break;
> @@ -4333,8 +4328,7 @@ xfs_bmapi_write(
> * First, deal with the hole before the allocated space
> * that we found, if any.
> */
> - if ((need_alloc || wasdelay) &&
> - !(flags & XFS_BMAPI_CONVERT_ONLY)) {
> + if (need_alloc || wasdelay) {
> bma.eof = eof;
> bma.conv = !!(flags & XFS_BMAPI_CONVERT);
> bma.wasdel = wasdelay;
> diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
> index f9a925caa70e..ee3848680684 100644
> --- a/fs/xfs/libxfs/xfs_bmap.h
> +++ b/fs/xfs/libxfs/xfs_bmap.h
> @@ -98,9 +98,6 @@ struct xfs_extent_free_item
> /* Only convert delalloc space, don't allocate entirely new extents */
> #define XFS_BMAPI_DELALLOC 0x400
>
> -/* Only convert unwritten extents, don't allocate new blocks */
> -#define XFS_BMAPI_CONVERT_ONLY 0x800
> -
> /* Skip online discard of freed extents */
> #define XFS_BMAPI_NODISCARD 0x1000
>
> @@ -118,7 +115,6 @@ struct xfs_extent_free_item
> { XFS_BMAPI_REMAP, "REMAP" }, \
> { XFS_BMAPI_COWFORK, "COWFORK" }, \
> { XFS_BMAPI_DELALLOC, "DELALLOC" }, \
> - { XFS_BMAPI_CONVERT_ONLY, "CONVERT_ONLY" }, \
> { XFS_BMAPI_NODISCARD, "NODISCARD" }, \
> { XFS_BMAPI_NORMAP, "NORMAP" }
>
> @@ -227,6 +223,10 @@ int xfs_bmapi_reserve_delalloc(struct xfs_inode *ip, int whichfork,
> xfs_fileoff_t off, xfs_filblks_t len, xfs_filblks_t prealloc,
> struct xfs_bmbt_irec *got, struct xfs_iext_cursor *cur,
> int eof);
> +int xfs_bmap_add_extent_unwritten_real(struct xfs_trans *tp,
> + struct xfs_inode *ip, int whichfork,
> + struct xfs_iext_cursor *icur, struct xfs_btree_cur **curp,
> + struct xfs_bmbt_irec *new, int *logflagsp);
>
> static inline void
> xfs_bmap_add_free(
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index d59b556d42cb..0cf13cb1b2fe 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -234,26 +234,42 @@ xfs_reflink_trim_around_shared(
> }
> }
>
> -/* Convert part of an unwritten CoW extent to a real one. */
> -STATIC int
> -xfs_reflink_convert_cow_extent(
> - struct xfs_inode *ip,
> - struct xfs_bmbt_irec *imap,
> - xfs_fileoff_t offset_fsb,
> - xfs_filblks_t count_fsb)
> +static int
> +xfs_reflink_convert_cow_locked(
> + struct xfs_inode *ip,
> + xfs_fileoff_t offset_fsb,
> + xfs_filblks_t count_fsb)
> {
> - int nimaps = 1;
> + struct xfs_iext_cursor icur;
> + struct xfs_bmbt_irec got;
> + struct xfs_btree_cur *dummy_cur = NULL;
> + int dummy_logflags;
> + int error;
>
> - if (imap->br_state == XFS_EXT_NORM)
> + if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
> return 0;
>
> - xfs_trim_extent(imap, offset_fsb, count_fsb);
> - trace_xfs_reflink_convert_cow(ip, imap);
> - if (imap->br_blockcount == 0)
> - return 0;
> - return xfs_bmapi_write(NULL, ip, imap->br_startoff, imap->br_blockcount,
> - XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT, 0, imap,
> - &nimaps);
> + do {
> + if (got.br_startoff >= offset_fsb + count_fsb)
> + break;
> + if (got.br_state == XFS_EXT_NORM)
> + continue;
> + if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))
> + return -EIO;
> +
> + xfs_trim_extent(&got, offset_fsb, count_fsb);
> + if (!got.br_blockcount)
> + continue;
> +
> + got.br_state = XFS_EXT_NORM;
> + error = xfs_bmap_add_extent_unwritten_real(NULL, ip,
> + XFS_COW_FORK, &icur, &dummy_cur, &got,
> + &dummy_logflags);
> + if (error)
> + return error;
> + } while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));
> +
> + return error;
> }
>
> /* Convert all of the unwritten CoW extents in a file's range to real ones. */
> @@ -267,15 +283,12 @@ xfs_reflink_convert_cow(
> xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
> xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
> xfs_filblks_t count_fsb = end_fsb - offset_fsb;
> - struct xfs_bmbt_irec imap;
> - int nimaps = 1, error = 0;
> + int error;
>
> ASSERT(count != 0);
>
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> - error = xfs_bmapi_write(NULL, ip, offset_fsb, count_fsb,
> - XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT |
> - XFS_BMAPI_CONVERT_ONLY, 0, &imap, &nimaps);
> + error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
At this point you might as well convert the one remaining caller of
xfs_reflink_convert_cow to take and drop the ILOCK around the
reflink_convert_cow call...
--D
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> return error;
> }
> @@ -405,9 +418,11 @@ xfs_reflink_allocate_cow(
> if (nimaps == 0)
> return -ENOSPC;
> convert:
> - if (!(flags & IOMAP_DIRECT))
> + xfs_trim_extent(imap, offset_fsb, count_fsb);
> + if (!(flags & IOMAP_DIRECT) || imap->br_state == XFS_EXT_NORM)
> return 0;
> - return xfs_reflink_convert_cow_extent(ip, imap, offset_fsb, count_fsb);
> + trace_xfs_reflink_convert_cow(ip, imap);
> + return xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
>
> out_unreserve:
> xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,
> --
> 2.19.1
>
