From: John Garry <john.g.garry@oracle.com> mainline inclusion from mainline-v6.15-rc2 commit 11ab31909d7cc177fab981cd0d6822a570244599 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/ID2HML CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- For when large atomic writes (> 1x FS block) are supported, there will be various occasions when HW offload may not be possible. Such instances include: - unaligned extent mapping wrt write length - extent mappings which do not cover the full write, e.g. the write spans sparse or mixed-mapping extents - the write length is greater than HW offload can support - no hardware support at all In those cases, we need to fallback to the CoW-based atomic write mode. For this, report special code -ENOPROTOOPT to inform the caller that HW offload-based method is not possible. In addition to the occasions mentioned, if the write covers an unallocated range, we again judge that we need to rely on the CoW-based method when we would need to allocate anything more than 1x block. This is because if we allocate less blocks that is required for the write, then again HW offload-based method would not be possible. So we are taking a pessimistic approach to writes covering unallocated space. Reviewed-by: Darrick J. Wong <djwong@kernel.org> [djwong: various cleanups] Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: John Garry <john.g.garry@oracle.com> Conflicts: fs/xfs/xfs_iomap.c Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/xfs/xfs_iomap.c | 62 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 60 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 4a7aef38d835..0cd69c08e897 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -763,6 +763,38 @@ imap_spans_range( return true; } +static bool +xfs_bmap_hw_atomic_write_possible( + struct xfs_inode *ip, + struct xfs_bmbt_irec *imap, + xfs_fileoff_t offset_fsb, + xfs_fileoff_t end_fsb) +{ + struct xfs_mount *mp = ip->i_mount; + xfs_fsize_t len = XFS_FSB_TO_B(mp, end_fsb - offset_fsb); + + /* + * atomic writes are required to be naturally aligned for disk blocks, + * which ensures that we adhere to block layer rules that we won't + * straddle any boundary or violate write alignment requirement. + */ + if (!IS_ALIGNED(imap->br_startblock, imap->br_blockcount)) + return false; + + /* + * Spanning multiple extents would mean that multiple BIOs would be + * issued, and so would lose atomicity required for REQ_ATOMIC-based + * atomics. + */ + if (!imap_spans_range(imap, offset_fsb, end_fsb)) + return false; + + /* + * The ->iomap_begin caller should ensure this, but check anyway. + */ + return len <= xfs_inode_buftarg(ip)->bt_bdev_awu_max; +} + static int xfs_direct_write_iomap_begin( struct inode *inode, @@ -777,9 +809,11 @@ xfs_direct_write_iomap_begin( struct xfs_bmbt_irec imap, cmap; xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset); xfs_fileoff_t end_fsb = xfs_iomap_end_fsb(mp, offset, length); + xfs_fileoff_t orig_end_fsb = end_fsb; int nimaps = 1, error = 0; bool shared = false; u16 iomap_flags = 0; + bool needs_alloc; unsigned int lockmode = XFS_ILOCK_SHARED; u64 seq; @@ -820,13 +854,37 @@ xfs_direct_write_iomap_begin( (flags & IOMAP_DIRECT) || IS_DAX(inode)); if (error) goto out_unlock; - if (shared) + if (shared) { + if ((flags & IOMAP_ATOMIC) && + !xfs_bmap_hw_atomic_write_possible(ip, &cmap, + offset_fsb, end_fsb)) { + error = -ENOPROTOOPT; + goto out_unlock; + } goto out_found_cow; + } end_fsb = imap.br_startoff + imap.br_blockcount; length = XFS_FSB_TO_B(mp, end_fsb) - offset; } - if (imap_needs_alloc(inode, flags, &imap, nimaps)) + needs_alloc = imap_needs_alloc(inode, flags, &imap, nimaps); + + if (flags & IOMAP_ATOMIC) { + error = -ENOPROTOOPT; + /* + * If we allocate less than what is required for the write + * then we may end up with multiple extents, which means that + * REQ_ATOMIC-based cannot be used, so avoid this possibility. + */ + if (needs_alloc && orig_end_fsb - offset_fsb > 1) + goto out_unlock; + + if (!xfs_bmap_hw_atomic_write_possible(ip, &imap, offset_fsb, + orig_end_fsb)) + goto out_unlock; + } + + if (needs_alloc) goto allocate_blocks; /* -- 2.39.2