ceph: introduce i_truncate_mutex
I encountered below deadlock when running fsstress
wmtruncate work truncate MDS
--------------- ------------------ --------------------------
lock i_mutex
<- truncate file
lock i_mutex (blocked)
<- revoking Fcb (filelock to MIX)
send request ->
handle request (xlock filelock)
At the initial time, there are some dirty pages in the page cache.
When the kclient receives the truncate message, it reduces inode size
and creates some 'out of i_size' dirty pages. wmtruncate work can't
truncate these dirty pages because it's blocked by the i_mutex. Later
when the kclient receives the cap message that revokes Fcb caps, It
can't flush all dirty pages because writepages() only flushes dirty
pages within the inode size.
When the MDS handles the 'truncate' request from kclient, it waits
for the filelock to become stable. But the filelock is stuck in
unstable state because it can't finish revoking kclient's Fcb caps.
The truncate pagecache locking has already caused lots of trouble
for use. I think it's time simplify it by introducing a new mutex.
We use the new mutex to prevent concurrent truncate_inode_pages().
There is no need to worry about race between buffered write and
truncate_inode_pages(), because our "get caps" mechanism prevents
them from concurrent execution.
Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 430121a..0e94d27 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2072,11 +2072,7 @@
/* finish pending truncate */
while (ci->i_truncate_pending) {
spin_unlock(&ci->i_ceph_lock);
- if (!(need & CEPH_CAP_FILE_WR))
- mutex_lock(&inode->i_mutex);
__ceph_do_pending_vmtruncate(inode);
- if (!(need & CEPH_CAP_FILE_WR))
- mutex_unlock(&inode->i_mutex);
spin_lock(&ci->i_ceph_lock);
}
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index bc07354..abc0e07 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -773,6 +773,13 @@
goto retry_snap;
}
} else {
+ /*
+ * No need to acquire the i_truncate_mutex. Because
+ * the MDS revokes Fwb caps before sending truncate
+ * message to us. We can't get Fwb cap while there
+ * are pending vmtruncate. So write and vmtruncate
+ * can not run at the same time
+ */
written = generic_file_buffered_write(iocb, iov, nr_segs,
pos, &iocb->ki_pos,
count, 0);
@@ -819,7 +826,6 @@
int ret;
mutex_lock(&inode->i_mutex);
- __ceph_do_pending_vmtruncate(inode);
if (whence == SEEK_END || whence == SEEK_DATA || whence == SEEK_HOLE) {
ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 98b6e50..602ccd8 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -352,6 +352,7 @@
for (i = 0; i < CEPH_FILE_MODE_NUM; i++)
ci->i_nr_by_mode[i] = 0;
+ mutex_init(&ci->i_truncate_mutex);
ci->i_truncate_seq = 0;
ci->i_truncate_size = 0;
ci->i_truncate_pending = 0;
@@ -463,16 +464,20 @@
dout("truncate_seq %u -> %u\n",
ci->i_truncate_seq, truncate_seq);
ci->i_truncate_seq = truncate_seq;
+
+ /* the MDS should have revoked these caps */
+ WARN_ON_ONCE(issued & (CEPH_CAP_FILE_EXCL |
+ CEPH_CAP_FILE_RD |
+ CEPH_CAP_FILE_WR |
+ CEPH_CAP_FILE_LAZYIO));
/*
* If we hold relevant caps, or in the case where we're
* not the only client referencing this file and we
* don't hold those caps, then we need to check whether
* the file is either opened or mmaped
*/
- if ((issued & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_RD|
- CEPH_CAP_FILE_WR|CEPH_CAP_FILE_BUFFER|
- CEPH_CAP_FILE_EXCL|
- CEPH_CAP_FILE_LAZYIO)) ||
+ if ((issued & (CEPH_CAP_FILE_CACHE|
+ CEPH_CAP_FILE_BUFFER)) ||
mapping_mapped(inode->i_mapping) ||
__ceph_caps_file_wanted(ci)) {
ci->i_truncate_pending++;
@@ -1427,18 +1432,20 @@
u32 orig_gen;
int check = 0;
+ mutex_lock(&ci->i_truncate_mutex);
spin_lock(&ci->i_ceph_lock);
dout("invalidate_pages %p gen %d revoking %d\n", inode,
ci->i_rdcache_gen, ci->i_rdcache_revoking);
if (ci->i_rdcache_revoking != ci->i_rdcache_gen) {
/* nevermind! */
spin_unlock(&ci->i_ceph_lock);
+ mutex_unlock(&ci->i_truncate_mutex);
goto out;
}
orig_gen = ci->i_rdcache_gen;
spin_unlock(&ci->i_ceph_lock);
- truncate_inode_pages(&inode->i_data, 0);
+ truncate_inode_pages(inode->i_mapping, 0);
spin_lock(&ci->i_ceph_lock);
if (orig_gen == ci->i_rdcache_gen &&
@@ -1453,6 +1460,7 @@
ci->i_rdcache_revoking);
}
spin_unlock(&ci->i_ceph_lock);
+ mutex_unlock(&ci->i_truncate_mutex);
if (check)
ceph_check_caps(ci, 0, NULL);
@@ -1473,16 +1481,7 @@
struct inode *inode = &ci->vfs_inode;
dout("vmtruncate_work %p\n", inode);
- if (!mutex_trylock(&inode->i_mutex)) {
- /*
- * the i_mutex can be hold by a writer who is waiting for
- * caps. wake up waiters, they will do pending vmtruncate.
- */
- wake_up_all(&ci->i_cap_wq);
- mutex_lock(&inode->i_mutex);
- }
__ceph_do_pending_vmtruncate(inode);
- mutex_unlock(&inode->i_mutex);
iput(inode);
}
@@ -1515,11 +1514,13 @@
u64 to;
int wrbuffer_refs, finish = 0;
+ mutex_lock(&ci->i_truncate_mutex);
retry:
spin_lock(&ci->i_ceph_lock);
if (ci->i_truncate_pending == 0) {
dout("__do_pending_vmtruncate %p none pending\n", inode);
spin_unlock(&ci->i_ceph_lock);
+ mutex_unlock(&ci->i_truncate_mutex);
return;
}
@@ -1536,6 +1537,9 @@
goto retry;
}
+ /* there should be no reader or writer */
+ WARN_ON_ONCE(ci->i_rd_ref || ci->i_wr_ref);
+
to = ci->i_truncate_size;
wrbuffer_refs = ci->i_wrbuffer_ref;
dout("__do_pending_vmtruncate %p (%d) to %lld\n", inode,
@@ -1553,6 +1557,8 @@
if (!finish)
goto retry;
+ mutex_unlock(&ci->i_truncate_mutex);
+
if (wrbuffer_refs == 0)
ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
@@ -1601,8 +1607,6 @@
if (ceph_snap(inode) != CEPH_NOSNAP)
return -EROFS;
- __ceph_do_pending_vmtruncate(inode);
-
err = inode_change_ok(inode, attr);
if (err != 0)
return err;
@@ -1783,7 +1787,8 @@
ceph_cap_string(dirtied), mask);
ceph_mdsc_put_request(req);
- __ceph_do_pending_vmtruncate(inode);
+ if (mask & CEPH_SETATTR_SIZE)
+ __ceph_do_pending_vmtruncate(inode);
return err;
out:
spin_unlock(&ci->i_ceph_lock);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index afcd62a6..f1e4e47 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -288,6 +288,7 @@
int i_nr_by_mode[CEPH_FILE_MODE_NUM]; /* open file counts */
+ struct mutex i_truncate_mutex;
u32 i_truncate_seq; /* last truncate to smaller size */
u64 i_truncate_size; /* and the size we last truncated down to */
int i_truncate_pending; /* still need to call vmtruncate */