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Subject[PATCH 19/21] staging: lustre: fid: fix up debugfs access to ->lcs_space
lcs_space can change while the lock is not held
if an RPC in underway. This can be detected by
seq->ls_update being set.

In this case, reading or writing the value should return
-EBUSY.

Also, the D_INFO CDEBUG() which reports the lcs_space being
updated never fires, as it tests the wrong value -
ldebugfs_fid_write_common() returns 'count' on success.

Finally, this return value should be returned from
ldebugfs_fid_space_seq_write(), rather than always returning 'count',
so that errors can be detected.

Signed-off-by: NeilBrown <neilb@suse.com>
---
drivers/staging/lustre/lustre/fid/lproc_fid.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/lustre/lustre/fid/lproc_fid.c b/drivers/staging/lustre/lustre/fid/lproc_fid.c
index e05487662afd..a1e5bf9f36ec 100644
--- a/drivers/staging/lustre/lustre/fid/lproc_fid.c
+++ b/drivers/staging/lustre/lustre/fid/lproc_fid.c
@@ -106,28 +106,35 @@ ldebugfs_fid_space_seq_write(struct file *file,
rc = ldebugfs_fid_write_common(buffer, count, &range);

spin_lock(&seq->lcs_lock);
+ if (seq->lcs_update)
+ /* An RPC call is active to update lcs_space */
+ rc = -EBUSY;
if (rc > 0)
seq->lcs_space = range;
spin_unlock(&seq->lcs_lock);

- if (rc == 0) {
+ if (rc > 0) {
CDEBUG(D_INFO, "%s: Space: " DRANGE "\n",
seq->lcs_name, PRANGE(&range));
}

- return count;
+ return rc;
}

static int
ldebugfs_fid_space_seq_show(struct seq_file *m, void *unused)
{
struct lu_client_seq *seq = (struct lu_client_seq *)m->private;
+ int rc = 0;

spin_lock(&seq->lcs_lock);
- seq_printf(m, "[%#llx - %#llx]:%x:%s\n", PRANGE(&seq->lcs_space));
+ if (seq->lcs_update)
+ rc = -EBUSY;
+ else
+ seq_printf(m, "[%#llx - %#llx]:%x:%s\n", PRANGE(&seq->lcs_space));
spin_unlock(&seq->lcs_lock);

- return 0;
+ return rc;
}

static ssize_t

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