From d39a2ced0fa0172faa46df0866fc22419b876e2a Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Thu, 17 Apr 2014 08:15:25 +1000 Subject: [PATCH] xfs: collapse range is delalloc challenged FSX has been detecting data corruption after to collapse range calls. The key observation is that the offset of the last extent in the file was not being shifted, and hence when the file size was adjusted it was truncating away data because the extents handled been correctly shifted. Tracing indicated that before the collapse, the extent list looked like: .... ino 0x5788 state idx 6 offset 26 block 195904 count 10 flag 0 ino 0x5788 state idx 7 offset 39 block 195917 count 35 flag 0 ino 0x5788 state idx 8 offset 86 block 195964 count 32 flag 0 and after the shift of 2 blocks: ino 0x5788 state idx 6 offset 24 block 195904 count 10 flag 0 ino 0x5788 state idx 7 offset 37 block 195917 count 35 flag 0 ino 0x5788 state idx 8 offset 86 block 195964 count 32 flag 0 Note that the last extent did not change offset. After the changing of the file size: ino 0x5788 state idx 6 offset 24 block 195904 count 10 flag 0 ino 0x5788 state idx 7 offset 37 block 195917 count 35 flag 0 ino 0x5788 state idx 8 offset 86 block 195964 count 30 flag 0 You can see that the last extent had it's length truncated, indicating that we've lost data. The reason for this is that the xfs_bmap_shift_extents() loop uses XFS_IFORK_NEXTENTS() to determine how many extents are in the inode. This, unfortunately, doesn't take into account delayed allocation extents - it's a count of physically allocated extents - and hence when the file being collapsed has a delalloc extent like this one does prior to the range being collapsed: .... ino 0x5788 state idx 4 offset 11 block 4503599627239429 count 1 flag 0 .... it gets the count wrong and terminates the shift loop early. Fix it by using the in-memory extent array size that includes delayed allocation extents to determine the number of extents on the inode. Signed-off-by: Dave Chinner Tested-by: Brian Foster Reviewed-by: Christoph Hellwig Signed-off-by: Dave Chinner --- fs/xfs/xfs_bmap.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c index 5b6092ef51ef..f0efc7e970ef 100644 --- a/fs/xfs/xfs_bmap.c +++ b/fs/xfs/xfs_bmap.c @@ -5413,6 +5413,7 @@ xfs_bmap_shift_extents( int whichfork = XFS_DATA_FORK; int logflags; xfs_filblks_t blockcount = 0; + int total_extents; if (unlikely(XFS_TEST_ERROR( (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS && @@ -5429,7 +5430,6 @@ xfs_bmap_shift_extents( ASSERT(current_ext != NULL); ifp = XFS_IFORK_PTR(ip, whichfork); - if (!(ifp->if_flags & XFS_IFEXTENTS)) { /* Read in all the extents */ error = xfs_iread_extents(tp, ip, whichfork); @@ -5456,7 +5456,6 @@ xfs_bmap_shift_extents( /* We are going to change core inode */ logflags = XFS_ILOG_CORE; - if (ifp->if_flags & XFS_IFBROOT) { cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork); cur->bc_private.b.firstblock = *firstblock; @@ -5467,8 +5466,14 @@ xfs_bmap_shift_extents( logflags |= XFS_ILOG_DEXT; } - while (nexts++ < num_exts && - *current_ext < XFS_IFORK_NEXTENTS(ip, whichfork)) { + /* + * There may be delalloc extents in the data fork before the range we + * are collapsing out, so we cannot + * use the count of real extents here. Instead we have to calculate it + * from the incore fork. + */ + total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t); + while (nexts++ < num_exts && *current_ext < total_extents) { gotp = xfs_iext_get_ext(ifp, *current_ext); xfs_bmbt_get_all(gotp, &got); @@ -5556,10 +5561,11 @@ xfs_bmap_shift_extents( } (*current_ext)++; + total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t); } /* Check if we are done */ - if (*current_ext == XFS_IFORK_NEXTENTS(ip, whichfork)) + if (*current_ext == total_extents) *done = 1; del_cursor: @@ -5568,6 +5574,5 @@ del_cursor: error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR); xfs_trans_log_inode(tp, ip, logflags); - return error; } -- 2.20.1