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gfs2: Move the inode glock locking to gfs2_file_buffered_write 

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>
This commit is contained in:
Andreas Gruenbacher 2021-08-11 21:50:14 +02:00
parent dc732906c2
commit b924bdab74
2 changed files with 28 additions and 59 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
fs/gfs2/bmap.c
View File

@ -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 *inode, loff_t pos, loff_t length,
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 *inode, loff_t pos, loff_t length,
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 *inode, loff_t pos, loff_t length,
}
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;
}

27
fs/gfs2/file.c
View File

@ -880,13 +880,40 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb, struct iov_iter *fro
{
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;
}