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Subject[PATCH 217/241] GFS2: Don't call file_accessed() with a shared glock
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3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Marzinski <bmarzins@redhat.com>

commit 3d1626889a64bd5a661544d582036a0a02104a60 upstream.

file_accessed() was being called by gfs2_mmap() with a shared glock. If it
needed to update the atime, it was crashing because it dirtied the inode in
gfs2_dirty_inode() without holding an exclusive lock. gfs2_dirty_inode()
checked if the caller was already holding a glock, but it didn't make sure that
the glock was in the exclusive state. Now, instead of calling file_accessed()
while holding the shared lock in gfs2_mmap(), file_accessed() is called after
grabbing and releasing the glock to update the inode. If file_accessed() needs
to update the atime, it will grab an exclusive lock in gfs2_dirty_inode().

gfs2_dirty_inode() now also checks to make sure that if the calling process has
already locked the glock, it has an exclusive lock.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
fs/gfs2/file.c | 12 +++++-------
fs/gfs2/super.c | 3 ++-
2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 31b199f..a8a81d7 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -492,15 +492,13 @@ static int gfs2_mmap(struct file *file, struct vm_area_struct *vma)
struct gfs2_holder i_gh;
int error;

- gfs2_holder_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
- error = gfs2_glock_nq(&i_gh);
- if (error == 0) {
- file_accessed(file);
- gfs2_glock_dq(&i_gh);
- }
- gfs2_holder_uninit(&i_gh);
+ error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
+ &i_gh);
if (error)
return error;
+ /* grab lock to update inode */
+ gfs2_glock_dq_uninit(&i_gh);
+ file_accessed(file);
}
vma->vm_ops = &gfs2_vm_ops;
vma->vm_flags |= VM_CAN_NONLINEAR;
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 713e621..12769a2 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -800,7 +800,8 @@ static void gfs2_dirty_inode(struct inode *inode, int flags)
return;
}
need_unlock = 1;
- }
+ } else if (WARN_ON_ONCE(ip->i_gl->gl_state != LM_ST_EXCLUSIVE))
+ return;

if (current->journal_info == NULL) {
ret = gfs2_trans_begin(sdp, RES_DINODE, 0);
--
1.7.9.5


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