From 59e4293149106fb92530f8e56fa3992d8548c5e6 Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Wed, 14 Nov 2018 07:46:40 -0800 Subject: xfs: fix shared extent data corruption due to missing cow reservation Page writeback indirectly handles shared extents via the existence of overlapping COW fork blocks. If COW fork blocks exist, writeback always performs the associated copy-on-write regardless if the underlying blocks are actually shared. If the blocks are shared, then overlapping COW fork blocks must always exist. fstests shared/010 reproduces a case where a buffered write occurs over a shared block without performing the requisite COW fork reservation. This ultimately causes writeback to the shared extent and data corruption that is detected across md5 checks of the filesystem across a mount cycle. The problem occurs when a buffered write lands over a shared extent that crosses an extent size hint boundary and that also happens to have a partial COW reservation that doesn't cover the start and end blocks of the data fork extent. For example, a buffered write occurs across the file offset (in FSB units) range of [29, 57]. A shared extent exists at blocks [29, 35] and COW reservation already exists at blocks [32, 34]. After accommodating a COW extent size hint of 32 blocks and the existing reservation at offset 32, xfs_reflink_reserve_cow() allocates 32 blocks of reservation at offset 0 and returns with COW reservation across the range of [0, 34]. The associated data fork extent is still [29, 35], however, which isn't fully covered by the COW reservation. This leads to a buffered write at file offset 35 over a shared extent without associated COW reservation. Writeback eventually kicks in, performs an overwrite of the underlying shared block and causes the associated data corruption. Update xfs_reflink_reserve_cow() to accommodate the fact that a delalloc allocation request may not fully cover the extent in the data fork. Trim the data fork extent appropriately, just as is done for shared extent boundaries and/or existing COW reservations that happen to overlap the start of the data fork extent. This prevents shared/010 failures due to data corruption on reflink enabled filesystems. Signed-off-by: Brian Foster Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_reflink.c | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/xfs/xfs_reflink.c') diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c index ecdb086bc23e..c56bdbfcf7ae 100644 --- a/fs/xfs/xfs_reflink.c +++ b/fs/xfs/xfs_reflink.c @@ -296,6 +296,7 @@ xfs_reflink_reserve_cow( if (error) return error; + xfs_trim_extent(imap, got.br_startoff, got.br_blockcount); trace_xfs_reflink_cow_alloc(ip, &got); return 0; } -- cgit From 2c307174ab77e34645e75e12827646e044d273c3 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Mon, 19 Nov 2018 13:31:10 -0800 Subject: xfs: flush removing page cache in xfs_reflink_remap_prep On a sub-page block size filesystem, fsx is failing with a data corruption after a series of operations involving copying a file with the destination offset beyond EOF of the destination of the file: 8093(157 mod 256): TRUNCATE DOWN from 0x7a120 to 0x50000 ******WWWW 8094(158 mod 256): INSERT 0x25000 thru 0x25fff (0x1000 bytes) 8095(159 mod 256): COPY 0x18000 thru 0x1afff (0x3000 bytes) to 0x2f400 8096(160 mod 256): WRITE 0x5da00 thru 0x651ff (0x7800 bytes) HOLE 8097(161 mod 256): COPY 0x2000 thru 0x5fff (0x4000 bytes) to 0x6fc00 The second copy here is beyond EOF, and it is to sub-page (4k) but block aligned (1k) offset. The clone runs the EOF zeroing, landing in a pre-existing post-eof delalloc extent. This zeroes the post-eof extents in the page cache just fine, dirtying the pages correctly. The problem is that xfs_reflink_remap_prep() now truncates the page cache over the range that it is copying it to, and rounds that down to cover the entire start page. This removes the dirty page over the delalloc extent from the page cache without having written it back. Hence later, when the page cache is flushed, the page at offset 0x6f000 has not been written back and hence exposes stale data, which fsx trips over less than 10 operations later. Fix this by changing xfs_reflink_remap_prep() to use xfs_flush_unmap_range(). Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_bmap_util.c | 2 +- fs/xfs/xfs_bmap_util.h | 3 +++ fs/xfs/xfs_reflink.c | 17 +++++++++++++---- 3 files changed, 17 insertions(+), 5 deletions(-) (limited to 'fs/xfs/xfs_reflink.c') diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c index 167ff4297e5c..404e581f1ea1 100644 --- a/fs/xfs/xfs_bmap_util.c +++ b/fs/xfs/xfs_bmap_util.c @@ -1042,7 +1042,7 @@ out_trans_cancel: goto out_unlock; } -static int +int xfs_flush_unmap_range( struct xfs_inode *ip, xfs_off_t offset, diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h index 87363d136bb6..7a78229cf1a7 100644 --- a/fs/xfs/xfs_bmap_util.h +++ b/fs/xfs/xfs_bmap_util.h @@ -80,4 +80,7 @@ int xfs_bmap_count_blocks(struct xfs_trans *tp, struct xfs_inode *ip, int whichfork, xfs_extnum_t *nextents, xfs_filblks_t *count); +int xfs_flush_unmap_range(struct xfs_inode *ip, xfs_off_t offset, + xfs_off_t len); + #endif /* __XFS_BMAP_UTIL_H__ */ diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c index c56bdbfcf7ae..322a852ce284 100644 --- a/fs/xfs/xfs_reflink.c +++ b/fs/xfs/xfs_reflink.c @@ -1352,10 +1352,19 @@ xfs_reflink_remap_prep( if (ret) goto out_unlock; - /* Zap any page cache for the destination file's range. */ - truncate_inode_pages_range(&inode_out->i_data, - round_down(pos_out, PAGE_SIZE), - round_up(pos_out + *len, PAGE_SIZE) - 1); + /* + * If pos_out > EOF, we may have dirtied blocks between EOF and + * pos_out. In that case, we need to extend the flush and unmap to cover + * from EOF to the end of the copy length. + */ + if (pos_out > XFS_ISIZE(dest)) { + loff_t flen = *len + (pos_out - XFS_ISIZE(dest)); + ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen); + } else { + ret = xfs_flush_unmap_range(dest, pos_out, *len); + } + if (ret) + goto out_unlock; return 1; out_unlock: -- cgit