From 450b1f6f56350c630e795f240dc5a77aa8aa2419 Mon Sep 17 00:00:00 2001 From: Andreas Gruenbacher Date: Thu, 29 Mar 2018 08:07:46 +0100 Subject: lockref: Add lockref_put_not_zero Put a lockref unless the lockref is dead or its count would become zero. This is the same as lockref_put_or_lock except that the lock is never left held. Signed-off-by: Andreas Gruenbacher Signed-off-by: Bob Peterson --- include/linux/lockref.h | 1 + lib/lockref.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 29 insertions(+) diff --git a/include/linux/lockref.h b/include/linux/lockref.h index 2eac32095113..99f17cc8e163 100644 --- a/include/linux/lockref.h +++ b/include/linux/lockref.h @@ -37,6 +37,7 @@ struct lockref { extern void lockref_get(struct lockref *); extern int lockref_put_return(struct lockref *); extern int lockref_get_not_zero(struct lockref *); +extern int lockref_put_not_zero(struct lockref *); extern int lockref_get_or_lock(struct lockref *); extern int lockref_put_or_lock(struct lockref *); diff --git a/lib/lockref.c b/lib/lockref.c index 47169ed7e964..3d468b53d4c9 100644 --- a/lib/lockref.c +++ b/lib/lockref.c @@ -80,6 +80,34 @@ int lockref_get_not_zero(struct lockref *lockref) } EXPORT_SYMBOL(lockref_get_not_zero); +/** + * lockref_put_not_zero - Decrements count unless count <= 1 before decrement + * @lockref: pointer to lockref structure + * Return: 1 if count updated successfully or 0 if count would become zero + */ +int lockref_put_not_zero(struct lockref *lockref) +{ + int retval; + + CMPXCHG_LOOP( + new.count--; + if (old.count <= 1) + return 0; + , + return 1; + ); + + spin_lock(&lockref->lock); + retval = 0; + if (lockref->count > 1) { + lockref->count--; + retval = 1; + } + spin_unlock(&lockref->lock); + return retval; +} +EXPORT_SYMBOL(lockref_put_not_zero); + /** * lockref_get_or_lock - Increments count unless the count is 0 or dead * @lockref: pointer to lockref structure -- cgit From 3fd5d3ad35dc44aaf0f28d60cc0eb75887bff54d Mon Sep 17 00:00:00 2001 From: Andreas Gruenbacher Date: Wed, 28 Mar 2018 12:05:35 +0200 Subject: gfs2: Stop using rhashtable_walk_peek Function rhashtable_walk_peek is problematic because there is no guarantee that the glock previously returned still exists; when that key is deleted, rhashtable_walk_peek can end up returning a different key, which will cause an inconsistent glock dump. Fix this by keeping track of the current glock in the seq file iterator functions instead. Signed-off-by: Andreas Gruenbacher Signed-off-by: Bob Peterson --- fs/gfs2/glock.c | 47 ++++++++++++++++++++++++++++------------------- 1 file changed, 28 insertions(+), 19 deletions(-) diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index 82fb5583445c..097bd3c0f270 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -1923,28 +1923,37 @@ void gfs2_glock_exit(void) static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi, loff_t n) { - if (n == 0) - gi->gl = rhashtable_walk_peek(&gi->hti); - else { - gi->gl = rhashtable_walk_next(&gi->hti); - n--; + struct gfs2_glock *gl = gi->gl; + + if (gl) { + if (n == 0) + return; + if (!lockref_put_not_zero(&gl->gl_lockref)) + gfs2_glock_queue_put(gl); } for (;;) { - if (IS_ERR_OR_NULL(gi->gl)) { - if (!gi->gl) - return; - if (PTR_ERR(gi->gl) != -EAGAIN) { - gi->gl = NULL; - return; + gl = rhashtable_walk_next(&gi->hti); + if (IS_ERR_OR_NULL(gl)) { + if (gl == ERR_PTR(-EAGAIN)) { + n = 1; + continue; } - n = 0; - } else if (gi->sdp == gi->gl->gl_name.ln_sbd && - !__lockref_is_dead(&gi->gl->gl_lockref)) { - if (!n--) - break; + gl = NULL; + break; + } + if (gl->gl_name.ln_sbd != gi->sdp) + continue; + if (n <= 1) { + if (!lockref_get_not_dead(&gl->gl_lockref)) + continue; + break; + } else { + if (__lockref_is_dead(&gl->gl_lockref)) + continue; + n--; } - gi->gl = rhashtable_walk_next(&gi->hti); } + gi->gl = gl; } static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos) @@ -1988,7 +1997,6 @@ static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr) { struct gfs2_glock_iter *gi = seq->private; - gi->gl = NULL; rhashtable_walk_stop(&gi->hti); } @@ -2076,7 +2084,8 @@ static int gfs2_glocks_release(struct inode *inode, struct file *file) struct seq_file *seq = file->private_data; struct gfs2_glock_iter *gi = seq->private; - gi->gl = NULL; + if (gi->gl) + gfs2_glock_put(gi->gl); rhashtable_walk_exit(&gi->hti); return seq_release_private(inode, file); } -- cgit From 3e7aafc39c59c639ebd5961f893743f076df9b4e Mon Sep 17 00:00:00 2001 From: Bob Peterson Date: Fri, 6 Apr 2018 13:07:45 -0700 Subject: GFS2: Minor improvements to comments and documentation This patch simply fixes some comments and the gfs2-glocks.txt file: Places where i_rwsem was called i_mutex, and adding i_rw_mutex. Signed-off-by: Bob Peterson --- Documentation/filesystems/gfs2-glocks.txt | 5 +++-- fs/gfs2/bmap.c | 2 +- fs/gfs2/ops_fstype.c | 2 +- 3 files changed, 5 insertions(+), 4 deletions(-) diff --git a/Documentation/filesystems/gfs2-glocks.txt b/Documentation/filesystems/gfs2-glocks.txt index 1fb12f9dfe48..7059623635b2 100644 --- a/Documentation/filesystems/gfs2-glocks.txt +++ b/Documentation/filesystems/gfs2-glocks.txt @@ -100,14 +100,15 @@ indicates that it is caching uptodate data. Glock locking order within GFS2: - 1. i_mutex (if required) + 1. i_rwsem (if required) 2. Rename glock (for rename only) 3. Inode glock(s) (Parents before children, inodes at "same level" with same parent in lock number order) 4. Rgrp glock(s) (for (de)allocation operations) 5. Transaction glock (via gfs2_trans_begin) for non-read operations - 6. Page lock (always last, very important!) + 6. i_rw_mutex (if required) + 7. Page lock (always last, very important!) There are two glocks per inode. One deals with access to the inode itself (locking order as above), and the other, known as the iopen diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c index 685c305cbeb6..278ed0869c3c 100644 --- a/fs/gfs2/bmap.c +++ b/fs/gfs2/bmap.c @@ -1744,7 +1744,7 @@ do_grow_qunlock: * @newsize: the size to make the file * * The file size can grow, shrink, or stay the same size. This - * is called holding i_mutex and an exclusive glock on the inode + * is called holding i_rwsem and an exclusive glock on the inode * in question. * * Returns: errno diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c index e6a0a8a89ea7..3ba3f167641c 100644 --- a/fs/gfs2/ops_fstype.c +++ b/fs/gfs2/ops_fstype.c @@ -825,7 +825,7 @@ static int init_inodes(struct gfs2_sbd *sdp, int undo) goto fail_rindex; } /* - * i_mutex on quota files is special. Since this inode is hidden system + * i_rwsem on quota files is special. Since this inode is hidden system * file, we are safe to define locking ourselves. */ lockdep_set_class(&sdp->sd_quota_inode->i_rwsem, -- cgit