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Thu, 13 Feb 2025 13:57:10 +0000 Received: from DM6PR10MB4313.namprd10.prod.outlook.com ([fe80::4f45:f4ab:121:e088]) by DM6PR10MB4313.namprd10.prod.outlook.com ([fe80::4f45:f4ab:121:e088%6]) with mapi id 15.20.8445.013; Thu, 13 Feb 2025 13:57:10 +0000 From: John Garry To: brauner@kernel.org, djwong@kernel.org, cem@kernel.org, dchinner@redhat.com, hch@lst.de Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ojaswin@linux.ibm.com, ritesh.list@gmail.com, martin.petersen@oracle.com, tytso@mit.edu, linux-ext4@vger.kernel.org, John Garry Subject: [PATCH v2 07/11] xfs: iomap CoW-based atomic write support Date: Thu, 13 Feb 2025 13:56:15 +0000 Message-Id: <20250213135619.1148432-8-john.g.garry@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20250213135619.1148432-1-john.g.garry@oracle.com> References: <20250213135619.1148432-1-john.g.garry@oracle.com> X-ClientProxiedBy: BN0PR04CA0044.namprd04.prod.outlook.com (2603:10b6:408:e8::19) To DM6PR10MB4313.namprd10.prod.outlook.com (2603:10b6:5:212::20) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6PR10MB4313:EE_|DS0PR10MB7125:EE_ X-MS-Office365-Filtering-Correlation-Id: 538b06f8-5069-40b7-f4e1-08dd4c364f7d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016; 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So, for that case, return -EAGAIN to request that the write be issued in CoW atomic write mode. The dio write path should detect this, similar to how misaligned regalar DIO writes are handled. For normal HW-based mode, when the range which we are atomic writing to covers a shared data extent, try to allocate a new CoW fork. However, if we find that what we allocated does not meet atomic write requirements in terms of length and alignment, then fallback on the CoW-based mode for the atomic write. Signed-off-by: John Garry --- fs/xfs/xfs_iomap.c | 72 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 69 insertions(+), 3 deletions(-) diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index ab79f0080288..c5ecfafbba60 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -795,6 +795,23 @@ imap_spans_range( return true; } +static bool +imap_range_valid_for_atomic_write( + struct xfs_bmbt_irec *imap, + xfs_fileoff_t offset_fsb, + xfs_fileoff_t end_fsb) +{ + /* Misaligned start block wrt size */ + if (!IS_ALIGNED(imap->br_startblock, imap->br_blockcount)) + return false; + + /* Discontiguous or mixed extents */ + if (!imap_spans_range(imap, offset_fsb, end_fsb)) + return false; + + return true; +} + static int xfs_direct_write_iomap_begin( struct inode *inode, @@ -809,12 +826,20 @@ 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); + bool atomic_cow = flags & IOMAP_ATOMIC_COW; + bool atomic_hw = flags & IOMAP_ATOMIC_HW; int nimaps = 1, error = 0; bool shared = false; u16 iomap_flags = 0; + xfs_fileoff_t orig_offset_fsb; + xfs_fileoff_t orig_end_fsb; + bool needs_alloc; unsigned int lockmode; u64 seq; + orig_offset_fsb = offset_fsb; + orig_end_fsb = end_fsb; + ASSERT(flags & (IOMAP_WRITE | IOMAP_ZERO)); if (xfs_is_shutdown(mp)) @@ -832,7 +857,7 @@ xfs_direct_write_iomap_begin( * COW writes may allocate delalloc space or convert unwritten COW * extents, so we need to make sure to take the lock exclusively here. */ - if (xfs_is_cow_inode(ip)) + if (xfs_is_cow_inode(ip) || atomic_cow) lockmode = XFS_ILOCK_EXCL; else lockmode = XFS_ILOCK_SHARED; @@ -857,6 +882,22 @@ xfs_direct_write_iomap_begin( if (error) goto out_unlock; + if (flags & IOMAP_ATOMIC_COW) { + error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared, + &lockmode, + (flags & IOMAP_DIRECT) || IS_DAX(inode), true); + /* + * Don't check @shared. For atomic writes, we should error when + * we don't get a CoW fork. + */ + if (error) + goto out_unlock; + + end_fsb = imap.br_startoff + imap.br_blockcount; + length = XFS_FSB_TO_B(mp, end_fsb) - offset; + goto out_found_cow; + } + if (imap_needs_cow(ip, flags, &imap, nimaps)) { error = -EAGAIN; if (flags & IOMAP_NOWAIT) @@ -868,13 +909,38 @@ xfs_direct_write_iomap_begin( (flags & IOMAP_DIRECT) || IS_DAX(inode), false); if (error) goto out_unlock; - if (shared) + if (shared) { + if (atomic_hw && + !imap_range_valid_for_atomic_write(&cmap, + orig_offset_fsb, orig_end_fsb)) { + error = -EAGAIN; + 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 (atomic_hw) { + error = -EAGAIN; + /* + * Use CoW method for when we need to alloc > 1 block, + * otherwise we might allocate less than what we need here and + * have multiple mappings. + */ + if (needs_alloc && orig_end_fsb - orig_offset_fsb > 1) + goto out_unlock; + + if (!imap_range_valid_for_atomic_write(&imap, orig_offset_fsb, + orig_end_fsb)) { + goto out_unlock; + } + } + + if (needs_alloc) goto allocate_blocks; /*