From 6321e3ed2acf3ee9643cdd403e1c88605d7944ba Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 24 Feb 2009 08:39:02 -0500 Subject: [PATCH] xfs: fix getbmap vs mmap deadlock xfs_getbmap (or rather the formatters called by it) copy out the getbmap structures under the ilock, which can deadlock against mmap. This has been reported via bugzilla a while ago (#717) and has recently also shown up via lockdep. So allocate a temporary buffer to format the kernel getbmap structures into and then copy them out after dropping the locks. A little problem with this is that we limit the number of extents we can copy out by the maximum allocation size, but I see no real way around that. Signed-off-by: Christoph Hellwig Reviewed-by: Eric Sandeen Reviewed-by: Felix Blyakher Signed-off-by: Felix Blyakher --- fs/xfs/xfs_bmap.c | 52 +++++++++++++++++++++++++++++++---------------- 1 file changed, 35 insertions(+), 17 deletions(-) diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c index abe42448b1c0..ca7c6005a487 100644 --- a/fs/xfs/xfs_bmap.c +++ b/fs/xfs/xfs_bmap.c @@ -5890,12 +5890,13 @@ xfs_getbmap( int nexleft; /* # of user extents left */ int subnex; /* # of bmapi's can do */ int nmap; /* number of map entries */ - struct getbmapx out; /* output structure */ + struct getbmapx *out; /* output structure */ int whichfork; /* data or attr fork */ int prealloced; /* this is a file with * preallocated data space */ int iflags; /* interface flags */ int bmapi_flags; /* flags for xfs_bmapi */ + int cur_ext = 0; mp = ip->i_mount; iflags = bmv->bmv_iflags; @@ -5971,6 +5972,13 @@ xfs_getbmap( return XFS_ERROR(EINVAL); bmvend = bmv->bmv_offset + bmv->bmv_length; + + if (bmv->bmv_count > ULONG_MAX / sizeof(struct getbmapx)) + return XFS_ERROR(ENOMEM); + out = kmem_zalloc(bmv->bmv_count * sizeof(struct getbmapx), KM_MAYFAIL); + if (!out) + return XFS_ERROR(ENOMEM); + xfs_ilock(ip, XFS_IOLOCK_SHARED); if (whichfork == XFS_DATA_FORK && !(iflags & BMV_IF_DELALLOC)) { if (ip->i_delayed_blks || ip->i_size > ip->i_d.di_size) { @@ -6025,39 +6033,39 @@ xfs_getbmap( ASSERT(nmap <= subnex); for (i = 0; i < nmap && nexleft && bmv->bmv_length; i++) { - int full = 0; /* user array is full */ - - out.bmv_oflags = 0; + out[cur_ext].bmv_oflags = 0; if (map[i].br_state == XFS_EXT_UNWRITTEN) - out.bmv_oflags |= BMV_OF_PREALLOC; + out[cur_ext].bmv_oflags |= BMV_OF_PREALLOC; else if (map[i].br_startblock == DELAYSTARTBLOCK) - out.bmv_oflags |= BMV_OF_DELALLOC; - out.bmv_offset = XFS_FSB_TO_BB(mp, map[i].br_startoff); - out.bmv_length = XFS_FSB_TO_BB(mp, map[i].br_blockcount); - out.bmv_unused1 = out.bmv_unused2 = 0; + out[cur_ext].bmv_oflags |= BMV_OF_DELALLOC; + out[cur_ext].bmv_offset = + XFS_FSB_TO_BB(mp, map[i].br_startoff); + out[cur_ext].bmv_length = + XFS_FSB_TO_BB(mp, map[i].br_blockcount); + out[cur_ext].bmv_unused1 = 0; + out[cur_ext].bmv_unused2 = 0; ASSERT(((iflags & BMV_IF_DELALLOC) != 0) || (map[i].br_startblock != DELAYSTARTBLOCK)); if (map[i].br_startblock == HOLESTARTBLOCK && whichfork == XFS_ATTR_FORK) { /* came to the end of attribute fork */ - out.bmv_oflags |= BMV_OF_LAST; + out[cur_ext].bmv_oflags |= BMV_OF_LAST; goto out_free_map; } - if (!xfs_getbmapx_fix_eof_hole(ip, &out, prealloced, - bmvend, map[i].br_startblock)) + if (!xfs_getbmapx_fix_eof_hole(ip, &out[cur_ext], + prealloced, bmvend, + map[i].br_startblock)) goto out_free_map; - /* format results & advance arg */ - error = formatter(&arg, &out, &full); - if (error || full) - goto out_free_map; nexleft--; bmv->bmv_offset = - out.bmv_offset + out.bmv_length; + out[cur_ext].bmv_offset + + out[cur_ext].bmv_length; bmv->bmv_length = max_t(__int64_t, 0, bmvend - bmv->bmv_offset); bmv->bmv_entries++; + cur_ext++; } } while (nmap && nexleft && bmv->bmv_length); @@ -6067,6 +6075,16 @@ xfs_getbmap( xfs_iunlock_map_shared(ip, lock); out_unlock_iolock: xfs_iunlock(ip, XFS_IOLOCK_SHARED); + + for (i = 0; i < cur_ext; i++) { + int full = 0; /* user array is full */ + + /* format results & advance arg */ + error = formatter(&arg, &out[i], &full); + if (error || full) + break; + } + return error; } -- 2.20.1