From 6bfb3d065f4c498c17a3a07f3dc08cedff53aff4 Mon Sep 17 00:00:00 2001 From: David Chinner Date: Thu, 30 Oct 2008 18:32:43 +1100 Subject: [PATCH] [XFS] Fix race when looking up reclaimable inodes If we get a race looking up a reclaimable inode, we can end up with the winner proceeding to use the inode before it has been completely re-initialised. This is a Bad Thing. Fix the race by checking whether we are still initialising the inod eonce we have a reference to it, and if so wait for the initialisation to complete before continuing. While there, fix a leaked reference count in the same code when encountering an unlinked inode and we are not doing a lookup for a create operation. SGI-PV: 987246 SGI-Modid: xfs-linux-melb:xfs-kern:32429a Signed-off-by: David Chinner Signed-off-by: Lachlan McIlroy --- fs/xfs/linux-2.6/xfs_linux.h | 1 + fs/xfs/xfs_iget.c | 32 ++++++++++++++++++++++---------- 2 files changed, 23 insertions(+), 10 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_linux.h b/fs/xfs/linux-2.6/xfs_linux.h index 214717650b23..77d6ddcaf547 100644 --- a/fs/xfs/linux-2.6/xfs_linux.h +++ b/fs/xfs/linux-2.6/xfs_linux.h @@ -77,6 +77,7 @@ #include #include #include +#include #include #include diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c index 837cae781536..bf4dc5eb4cfc 100644 --- a/fs/xfs/xfs_iget.c +++ b/fs/xfs/xfs_iget.c @@ -52,7 +52,7 @@ xfs_iget_cache_hit( int lock_flags) __releases(pag->pag_ici_lock) { struct xfs_mount *mp = ip->i_mount; - int error = 0; + int error = EAGAIN; /* * If INEW is set this inode is being set up @@ -60,7 +60,6 @@ xfs_iget_cache_hit( * Pause and try again. */ if (xfs_iflags_test(ip, (XFS_INEW|XFS_IRECLAIM))) { - error = EAGAIN; XFS_STATS_INC(xs_ig_frecycle); goto out_error; } @@ -73,7 +72,6 @@ xfs_iget_cache_hit( * error immediately so we don't remove it from the reclaim * list and potentially leak the inode. */ - if ((ip->i_d.di_mode == 0) && !(flags & XFS_IGET_CREATE)) { error = ENOENT; goto out_error; @@ -91,27 +89,42 @@ xfs_iget_cache_hit( error = ENOMEM; goto out_error; } + + /* + * We must set the XFS_INEW flag before clearing the + * XFS_IRECLAIMABLE flag so that if a racing lookup does + * not find the XFS_IRECLAIMABLE above but has the igrab() + * below succeed we can safely check XFS_INEW to detect + * that this inode is still being initialised. + */ xfs_iflags_set(ip, XFS_INEW); xfs_iflags_clear(ip, XFS_IRECLAIMABLE); /* clear the radix tree reclaim flag as well. */ __xfs_inode_clear_reclaim_tag(mp, pag, ip); - read_unlock(&pag->pag_ici_lock); } else if (!igrab(VFS_I(ip))) { /* If the VFS inode is being torn down, pause and try again. */ - error = EAGAIN; XFS_STATS_INC(xs_ig_frecycle); goto out_error; - } else { - /* we've got a live one */ - read_unlock(&pag->pag_ici_lock); + } else if (xfs_iflags_test(ip, XFS_INEW)) { + /* + * We are racing with another cache hit that is + * currently recycling this inode out of the XFS_IRECLAIMABLE + * state. Wait for the initialisation to complete before + * continuing. + */ + wait_on_inode(VFS_I(ip)); } if (ip->i_d.di_mode == 0 && !(flags & XFS_IGET_CREATE)) { error = ENOENT; - goto out; + iput(VFS_I(ip)); + goto out_error; } + /* We've got a live one. */ + read_unlock(&pag->pag_ici_lock); + if (lock_flags != 0) xfs_ilock(ip, lock_flags); @@ -122,7 +135,6 @@ xfs_iget_cache_hit( out_error: read_unlock(&pag->pag_ici_lock); -out: return error; } -- 2.34.1