Eric Lee / smarc-ti-linux-kernel

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Commit d038a63ace6cf2ce3aeafa741b73d542ffb65163

Authored by Linus Torvalds
2 parents cb95413971 f82c458a2c
Exists in ti-lsk-linux-4.1.y and in 10 other branches dlt-processor-sdk-linux-03.00.00.04, processor-sdk-linux-02.00.01, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 

Pull btrfs deadlock fix from Chris Mason:
 "This has a fix for a long standing deadlock that we've been trying to
  nail down for a while.  It ended up being a bad interaction with the
  fair reader/writer locks and the order btrfs reacquires locks in the
  btree"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  btrfs: fix lockups from btrfs_clear_path_blocking

Showing 3 changed files Side-by-side Diff

... ... @@ -80,13 +80,6 @@
80 80 {
81 81 int i;
82 82  
83   -#ifdef CONFIG_DEBUG_LOCK_ALLOC
84   - /* lockdep really cares that we take all of these spinlocks
85   - * in the right order. If any of the locks in the path are not
86   - * currently blocking, it is going to complain. So, make really
87   - * really sure by forcing the path to blocking before we clear
88   - * the path blocking.
89   - */
90 83 if (held) {
91 84 btrfs_set_lock_blocking_rw(held, held_rw);
92 85 if (held_rw == BTRFS_WRITE_LOCK)
... ... @@ -95,7 +88,6 @@
95 88 held_rw = BTRFS_READ_LOCK_BLOCKING;
96 89 }
97 90 btrfs_set_path_blocking(p);
98   -#endif
99 91  
100 92 for (i = BTRFS_MAX_LEVEL - 1; i >= 0; i--) {
101 93 if (p->nodes[i] && p->locks[i]) {
102 94  
... ... @@ -107,10 +99,8 @@
107 99 }
108 100 }
109 101  
110   -#ifdef CONFIG_DEBUG_LOCK_ALLOC
111 102 if (held)
112 103 btrfs_clear_lock_blocking_rw(held, held_rw);
113   -#endif
114 104 }
115 105  
116 106 /* this also releases the path */
... ... @@ -2893,7 +2883,7 @@
2893 2883 }
2894 2884 p->locks[level] = BTRFS_WRITE_LOCK;
2895 2885 } else {
2896   - err = btrfs_try_tree_read_lock(b);
  2886 + err = btrfs_tree_read_lock_atomic(b);
2897 2887 if (!err) {
2898 2888 btrfs_set_path_blocking(p);
2899 2889 btrfs_tree_read_lock(b);
... ... @@ -3025,7 +3015,7 @@
3025 3015 }
3026 3016  
3027 3017 level = btrfs_header_level(b);
3028   - err = btrfs_try_tree_read_lock(b);
  3018 + err = btrfs_tree_read_lock_atomic(b);
3029 3019 if (!err) {
3030 3020 btrfs_set_path_blocking(p);
3031 3021 btrfs_tree_read_lock(b);
... ... @@ -128,9 +128,29 @@
128 128 }
129 129  
130 130 /*
  131 + * take a spinning read lock.
131 132 * returns 1 if we get the read lock and 0 if we don't
132 133 * this won't wait for blocking writers
133 134 */
  135 +int btrfs_tree_read_lock_atomic(struct extent_buffer *eb)
  136 +{
  137 + if (atomic_read(&eb->blocking_writers))
  138 + return 0;
  139 +
  140 + read_lock(&eb->lock);
  141 + if (atomic_read(&eb->blocking_writers)) {
  142 + read_unlock(&eb->lock);
  143 + return 0;
  144 + }
  145 + atomic_inc(&eb->read_locks);
  146 + atomic_inc(&eb->spinning_readers);
  147 + return 1;
  148 +}
  149 +
  150 +/*
  151 + * returns 1 if we get the read lock and 0 if we don't
  152 + * this won't wait for blocking writers
  153 + */
134 154 int btrfs_try_tree_read_lock(struct extent_buffer *eb)
135 155 {
136 156 if (atomic_read(&eb->blocking_writers))
... ... @@ -158,9 +178,7 @@
158 178 atomic_read(&eb->blocking_readers))
159 179 return 0;
160 180  
161   - if (!write_trylock(&eb->lock))
162   - return 0;
163   -
  181 + write_lock(&eb->lock);
164 182 if (atomic_read(&eb->blocking_writers) ||
165 183 atomic_read(&eb->blocking_readers)) {
166 184 write_unlock(&eb->lock);
... ... @@ -35,6 +35,8 @@
35 35 void btrfs_assert_tree_locked(struct extent_buffer *eb);
36 36 int btrfs_try_tree_read_lock(struct extent_buffer *eb);
37 37 int btrfs_try_tree_write_lock(struct extent_buffer *eb);
  38 +int btrfs_tree_read_lock_atomic(struct extent_buffer *eb);
  39 +
38 40  
39 41 static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw)
40 42 {