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[PATCH 19/19] XFS: set PF_FSTRANS while ilock is held in xfs_free_eofblo

To: linux-mm@xxxxxxxxx, linux-nfs@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH 19/19] XFS: set PF_FSTRANS while ilock is held in xfs_free_eofblocks
From: NeilBrown <neilb@xxxxxxx>
Date: Wed, 16 Apr 2014 14:03:37 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140416033623.10604.69237.stgit@xxxxxxxxxxxxxx>
References: <20140416033623.10604.69237.stgit@xxxxxxxxxxxxxx>
User-agent: StGit/0.16
memory allocates can happen while the xfs ilock is held in
xfs_free_eofblocks, particularly

  [<ffffffff813e6667>] kmem_zone_alloc+0x67/0xc0
  [<ffffffff813e5945>] xfs_trans_add_item+0x25/0x50
  [<ffffffff8143d64c>] xfs_trans_ijoin+0x2c/0x60
  [<ffffffff8142275e>] xfs_itruncate_extents+0xbe/0x400
  [<ffffffff813c72f4>] xfs_free_eofblocks+0x1c4/0x240

So set PF_FSTRANS to avoid this causing a deadlock.

Care is needed here as xfs_trans_reserve() also sets PF_FSTRANS, while
xfs_trans_cancel and xfs_trans_commit will clear it.
So our extra setting must fully nest these calls.

Signed-off-by: NeilBrown <neilb@xxxxxxx>
 fs/xfs/xfs_bmap_util.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index f264616080ca..53761fe4fada 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -889,6 +889,7 @@ xfs_free_eofblocks(
        xfs_filblks_t   map_len;
        int             nimaps;
        xfs_bmbt_irec_t imap;
+       unsigned int pflags;
         * Figure out if there are any blocks beyond the end
@@ -929,12 +930,14 @@ xfs_free_eofblocks(
+               current_set_flags_nested(&pflags, PF_FSTRANS);
                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_itruncate, 0, 0);
                if (error) {
                        xfs_trans_cancel(tp, 0);
                        if (need_iolock)
                                xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+                       current_restore_flags_nested(&pflags, PF_FSTRANS);
                        return error;
@@ -964,6 +967,7 @@ xfs_free_eofblocks(
+               current_restore_flags_nested(&pflags, PF_FSTRANS);
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
                if (need_iolock)
                        xfs_iunlock(ip, XFS_IOLOCK_EXCL);

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