From b0d7c2231015b331b942746610a05b6ea72977ab Mon Sep 17 00:00:00 2001 From: "Yan, Zheng" Date: Mon, 12 Aug 2013 21:42:15 -0700 Subject: 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 Signed-off-by: Yan, Zheng --- fs/ceph/inode.c | 39 ++++++++++++++++++++++----------------- 1 file changed, 22 insertions(+), 17 deletions(-) (limited to 'fs/ceph/inode.c') 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 @@ struct inode *ceph_alloc_inode(struct super_block *sb) 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 @@ int ceph_fill_file_size(struct inode *inode, int issued, 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 @@ static void ceph_invalidate_work(struct work_struct *work) 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 @@ static void ceph_invalidate_work(struct work_struct *work) 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 @@ static void ceph_vmtruncate_work(struct work_struct *work) 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 @@ void __ceph_do_pending_vmtruncate(struct inode *inode) 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 @@ retry: 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 @@ retry: 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 @@ int ceph_setattr(struct dentry *dentry, struct iattr *attr) 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 @@ int ceph_setattr(struct dentry *dentry, struct iattr *attr) 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); -- cgit v1.1