[PATCH 5.15 21/33] gfs2: Move the inode glock locking to gfs2_file_buffered_write

Greg Kroah-Hartman
2022-04-29T10:45:01Z

From: Andreas Gruenbacher <agruenba@redhat.com>

commit b924bdab7445946e2ed364a0e6e249d36f1f1158 upstream

So far, for buffered writes, we were taking the inode glock in
gfs2_iomap_begin and dropping it in gfs2_iomap_end with the intention of
not holding the inode glock while iomap_write_actor faults in user
pages. It turns out that iomap_write_actor is called inside iomap_begin
... iomap_end, so the user pages were still faulted in while holding the
inode glock and the locking code in iomap_begin / iomap_end was
completely pointless.

Move the locking into gfs2_file_buffered_write instead. We'll take care
of the potential deadlocks due to faulting in user pages while holding a
glock in a subsequent patch.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/gfs2/bmap.c | 60 ---------------------------------------------------------
fs/gfs2/file.c | 27 +++++++++++++++++++++++++
2 files changed, 28 insertions(+), 59 deletions(-)

--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -961,46 +961,6 @@ hole_found:
goto out;
}

-static int gfs2_write_lock(struct inode *inode)
-{
- struct gfs2_inode *ip = GFS2_I(inode);
- struct gfs2_sbd *sdp = GFS2_SB(inode);
- int error;
-
- gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &ip->i_gh);
- error = gfs2_glock_nq(&ip->i_gh);
- if (error)
- goto out_uninit;
- if (&ip->i_inode == sdp->sd_rindex) {
- struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
-
- error = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE,
- GL_NOCACHE, &m_ip->i_gh);
- if (error)
- goto out_unlock;
- }
- return 0;
-
-out_unlock:
- gfs2_glock_dq(&ip->i_gh);
-out_uninit:
- gfs2_holder_uninit(&ip->i_gh);
- return error;
-}
-
-static void gfs2_write_unlock(struct inode *inode)
-{
- struct gfs2_inode *ip = GFS2_I(inode);
- struct gfs2_sbd *sdp = GFS2_SB(inode);
-
- if (&ip->i_inode == sdp->sd_rindex) {
- struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
-
- gfs2_glock_dq_uninit(&m_ip->i_gh);
- }
- gfs2_glock_dq_uninit(&ip->i_gh);
-}
-
static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos,
unsigned len)
{
@@ -1118,11 +1078,6 @@ out_qunlock:
return ret;
}

-static inline bool gfs2_iomap_need_write_lock(unsigned flags)
-{
- return (flags & IOMAP_WRITE) && !(flags & IOMAP_DIRECT);
-}
-
static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
unsigned flags, struct iomap *iomap,
struct iomap *srcmap)
@@ -1135,12 +1090,6 @@ static int gfs2_iomap_begin(struct inode
iomap->flags |= IOMAP_F_BUFFER_HEAD;

trace_gfs2_iomap_start(ip, pos, length, flags);
- if (gfs2_iomap_need_write_lock(flags)) {
- ret = gfs2_write_lock(inode);
- if (ret)
- goto out;
- }
-
ret = __gfs2_iomap_get(inode, pos, length, flags, iomap, &mp);
if (ret)
goto out_unlock;
@@ -1168,10 +1117,7 @@ static int gfs2_iomap_begin(struct inode
ret = gfs2_iomap_begin_write(inode, pos, length, flags, iomap, &mp);

out_unlock:
- if (ret && gfs2_iomap_need_write_lock(flags))
- gfs2_write_unlock(inode);
release_metapath(&mp);
-out:
trace_gfs2_iomap_end(ip, iomap, ret);
return ret;
}
@@ -1219,15 +1165,11 @@ static int gfs2_iomap_end(struct inode *
}

if (unlikely(!written))
- goto out_unlock;
+ return 0;

if (iomap->flags & IOMAP_F_SIZE_CHANGED)
mark_inode_dirty(inode);
set_bit(GLF_DIRTY, &ip->i_gl->gl_flags);
-
-out_unlock:
- if (gfs2_iomap_need_write_lock(flags))
- gfs2_write_unlock(inode);
return 0;
}

--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -881,13 +881,40 @@ static ssize_t gfs2_file_buffered_write(
{
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(file);
+ struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_sbd *sdp = GFS2_SB(inode);
ssize_t ret;

+ gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &ip->i_gh);
+ ret = gfs2_glock_nq(&ip->i_gh);
+ if (ret)
+ goto out_uninit;
+
+ if (inode == sdp->sd_rindex) {
+ struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
+
+ ret = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE,
+ GL_NOCACHE, &m_ip->i_gh);
+ if (ret)
+ goto out_unlock;
+ }
+
current->backing_dev_info = inode_to_bdi(inode);
ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
current->backing_dev_info = NULL;
if (ret > 0)
iocb->ki_pos += ret;
+
+ if (inode == sdp->sd_rindex) {
+ struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
+
+ gfs2_glock_dq_uninit(&m_ip->i_gh);
+ }
+
+out_unlock:
+ gfs2_glock_dq(&ip->i_gh);
+out_uninit:
+ gfs2_holder_uninit(&ip->i_gh);
return ret;
}