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[PATCH] xfs: simplify inode teardown

To: xfs@xxxxxxxxxxx
Subject: [PATCH] xfs: simplify inode teardown
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Tue, 29 Sep 2009 09:48:56 -0400
User-agent: Mutt/1.5.19 (2009-01-05)
Currently the reclaim code for the case where we don't reclaim the final
reclaim is overly complicated.  We know that the inode is clean but instead
of just directly reclaiming the clean inode we go through the whole
process of marking the inode reclaimable just to directly reclaim it
from the calling context.  Besides beeing overly complicated this introduces
a race where iget could recycle an inode between marked reclaimable and
actually beeing reclaimed leading to panics.

This patch gets rid of the existing reclaim path, and replaces it with a
simple call to xfs_ireclaim if the inode was clean.  While we're at it
we also use the slightly more lax xfs_inode_clean check we'd use later
to determine if we need to flush the inode here.

Finally get rid of xfs_reclaim function and place the remaining small
bits of reclaim code directly into xfs_fs_destroy_inode.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reported-by: Patrick Schreurs <patrick@xxxxxxxxxxxxxxxx>
Reported-by: Tommy van Leeuwen <tommy@xxxxxxxxxxxxxxxx>
Tested-by: Patrick Schreurs <patrick@xxxxxxxxxxxxxxxx>

Index: xfs/fs/xfs/xfs_vnodeops.c
===================================================================
--- xfs.orig/fs/xfs/xfs_vnodeops.c      2009-09-18 09:06:33.595274598 -0300
+++ xfs/fs/xfs/xfs_vnodeops.c   2009-09-18 09:07:30.437255826 -0300
@@ -2456,46 +2456,6 @@ xfs_set_dmattrs(
        return error;
 }
 
-int
-xfs_reclaim(
-       xfs_inode_t     *ip)
-{
-
-       xfs_itrace_entry(ip);
-
-       ASSERT(!VN_MAPPED(VFS_I(ip)));
-
-       /* bad inode, get out here ASAP */
-       if (is_bad_inode(VFS_I(ip))) {
-               xfs_ireclaim(ip);
-               return 0;
-       }
-
-       xfs_ioend_wait(ip);
-
-       ASSERT(XFS_FORCED_SHUTDOWN(ip->i_mount) || ip->i_delayed_blks == 0);
-
-       /*
-        * If we have nothing to flush with this inode then complete the
-        * teardown now, otherwise break the link between the xfs inode and the
-        * linux inode and clean up the xfs inode later. This avoids flushing
-        * the inode to disk during the delete operation itself.
-        *
-        * When breaking the link, we need to set the XFS_IRECLAIMABLE flag
-        * first to ensure that xfs_iunpin() will never see an xfs inode
-        * that has a linux inode being reclaimed. Synchronisation is provided
-        * by the i_flags_lock.
-        */
-       if (!ip->i_update_core && (ip->i_itemp == NULL)) {
-               xfs_ilock(ip, XFS_ILOCK_EXCL);
-               xfs_iflock(ip);
-               xfs_iflags_set(ip, XFS_IRECLAIMABLE);
-               return xfs_reclaim_inode(ip, 1, XFS_IFLUSH_DELWRI_ELSE_SYNC);
-       }
-       xfs_inode_set_reclaim_tag(ip);
-       return 0;
-}
-
 /*
  * xfs_alloc_file_space()
  *      This routine allocates disk space for the given file.
Index: xfs/fs/xfs/linux-2.6/xfs_super.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_super.c       2009-09-18 09:07:15.869281043 
-0300
+++ xfs/fs/xfs/linux-2.6/xfs_super.c    2009-09-18 09:12:39.301006661 -0300
@@ -930,13 +930,39 @@ xfs_fs_alloc_inode(
  */
 STATIC void
 xfs_fs_destroy_inode(
-       struct inode    *inode)
+       struct inode            *inode)
 {
-       xfs_inode_t             *ip = XFS_I(inode);
+       struct xfs_inode        *ip = XFS_I(inode);
+
+       xfs_itrace_entry(ip);
 
        XFS_STATS_INC(vn_reclaim);
-       if (xfs_reclaim(ip))
-               panic("%s: cannot reclaim 0x%p\n", __func__, inode);
+
+       /* bad inode, get out here ASAP */
+       if (is_bad_inode(inode))
+               goto out_reclaim;
+
+       xfs_ioend_wait(ip);
+
+       ASSERT(XFS_FORCED_SHUTDOWN(ip->i_mount) || ip->i_delayed_blks == 0);
+
+       /*
+        * We should never get here with one of the reclaim flags already set.
+        */
+       ASSERT_ALWAYS(!xfs_iflags_test(ip, XFS_IRECLAIMABLE));
+       ASSERT_ALWAYS(!xfs_iflags_test(ip, XFS_IRECLAIM));
+
+       /*
+        * If we have nothing to flush with this inode then complete the
+        * teardown now, otherwise delay the flush operation.
+        */
+       if (!xfs_inode_clean(ip)) {
+               xfs_inode_set_reclaim_tag(ip);
+               return;
+       }
+
+out_reclaim:
+       xfs_ireclaim(ip);
 }
 
 /*
Index: xfs/fs/xfs/xfs_vnodeops.h
===================================================================
--- xfs.orig/fs/xfs/xfs_vnodeops.h      2009-09-18 09:10:07.930003796 -0300
+++ xfs/fs/xfs/xfs_vnodeops.h   2009-09-18 09:10:11.789032549 -0300
@@ -38,7 +38,6 @@ int xfs_symlink(struct xfs_inode *dp, st
                const char *target_path, mode_t mode, struct xfs_inode **ipp,
                cred_t *credp);
 int xfs_set_dmattrs(struct xfs_inode *ip, u_int evmask, u_int16_t state);
-int xfs_reclaim(struct xfs_inode *ip);
 int xfs_change_file_space(struct xfs_inode *ip, int cmd,
                xfs_flock64_t *bf, xfs_off_t offset, int attr_flags);
 int xfs_rename(struct xfs_inode *src_dp, struct xfs_name *src_name,
Index: xfs/fs/xfs/linux-2.6/xfs_sync.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_sync.c        2009-09-18 09:13:28.627003540 
-0300
+++ xfs/fs/xfs/linux-2.6/xfs_sync.c     2009-09-18 09:22:33.861006462 -0300
@@ -663,10 +663,9 @@ xfs_syncd_stop(
        kthread_stop(mp->m_sync_task);
 }
 
-int
+STATIC int
 xfs_reclaim_inode(
        xfs_inode_t     *ip,
-       int             locked,
        int             sync_mode)
 {
        xfs_perag_t     *pag = xfs_get_perag(ip->i_mount, ip->i_ino);
@@ -682,10 +681,6 @@ xfs_reclaim_inode(
            !__xfs_iflags_test(ip, XFS_IRECLAIMABLE)) {
                spin_unlock(&ip->i_flags_lock);
                write_unlock(&pag->pag_ici_lock);
-               if (locked) {
-                       xfs_ifunlock(ip);
-                       xfs_iunlock(ip, XFS_ILOCK_EXCL);
-               }
                return -EAGAIN;
        }
        __xfs_iflags_set(ip, XFS_IRECLAIM);
@@ -704,10 +699,8 @@ xfs_reclaim_inode(
         * We get the flush lock regardless, though, just to make sure
         * we don't free it while it is being flushed.
         */
-       if (!locked) {
-               xfs_ilock(ip, XFS_ILOCK_EXCL);
-               xfs_iflock(ip);
-       }
+       xfs_ilock(ip, XFS_ILOCK_EXCL);
+       xfs_iflock(ip);
 
        /*
         * In the case of a forced shutdown we rely on xfs_iflush() to
@@ -778,7 +771,7 @@ xfs_reclaim_inode_now(
        }
        read_unlock(&pag->pag_ici_lock);
 
-       return xfs_reclaim_inode(ip, 0, flags);
+       return xfs_reclaim_inode(ip, flags);
 }
 
 int
Index: xfs/fs/xfs/linux-2.6/xfs_sync.h
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_sync.h        2009-09-18 09:13:28.639004162 
-0300
+++ xfs/fs/xfs/linux-2.6/xfs_sync.h     2009-09-18 09:13:38.354031011 -0300
@@ -44,7 +44,6 @@ void xfs_quiesce_attr(struct xfs_mount *
 
 void xfs_flush_inodes(struct xfs_inode *ip);
 
-int xfs_reclaim_inode(struct xfs_inode *ip, int locked, int sync_mode);
 int xfs_reclaim_inodes(struct xfs_mount *mp, int mode);
 
 void xfs_inode_set_reclaim_tag(struct xfs_inode *ip);

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