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authorThomas Gleixner <tglx@linutronix.de>2019-08-09 14:42:32 +0200
committerTheodore Ts'o <tytso@mit.edu>2019-10-21 09:16:46 -0400
commit464170647b5648bb81f3615567485fcb9a685bed (patch)
treecb8bee9bf114c269de6c405bdb0fcdafbd65dd76 /fs/ocfs2
parent2e710ff03fc4599059eeda68c8de2383e65af825 (diff)
downloadlinux-464170647b5648bb81f3615567485fcb9a685bed.tar.bz2
jbd2: Make state lock a spinlock
Bit-spinlocks are problematic on PREEMPT_RT if functions which might sleep on RT, e.g. spin_lock(), alloc/free(), are invoked inside the lock held region because bit spinlocks disable preemption even on RT. A first attempt was to replace state lock with a spinlock placed in struct buffer_head and make the locking conditional on PREEMPT_RT and DEBUG_BIT_SPINLOCKS. Jan pointed out that there is a 4 byte hole in struct journal_head where a regular spinlock fits in and he would not object to convert the state lock to a spinlock unconditionally. Aside of solving the RT problem, this also gains lockdep coverage for the journal head state lock (bit-spinlocks are not covered by lockdep as it's hard to fit a lockdep map into a single bit). The trivial change would have been to convert the jbd_*lock_bh_state() inlines, but that comes with the downside that these functions take a buffer head pointer which needs to be converted to a journal head pointer which adds another level of indirection. As almost all functions which use this lock have a journal head pointer readily available, it makes more sense to remove the lock helper inlines and write out spin_*lock() at all call sites. Fixup all locking comments as well. Suggested-by: Jan Kara <jack@suse.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Jan Kara <jack@suse.cz> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Mark Fasheh <mark@fasheh.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Jan Kara <jack@suse.com> Cc: linux-ext4@vger.kernel.org Link: https://lore.kernel.org/r/20190809124233.13277-7-jack@suse.cz Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ocfs2')
-rw-r--r--fs/ocfs2/suballoc.c19
1 files changed, 11 insertions, 8 deletions
diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index 69c21a3843af..4180c3ef0a68 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -1252,6 +1252,7 @@ static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,
int nr)
{
struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) bg_bh->b_data;
+ struct journal_head *jh;
int ret;
if (ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap))
@@ -1260,13 +1261,14 @@ static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,
if (!buffer_jbd(bg_bh))
return 1;
- jbd_lock_bh_state(bg_bh);
- bg = (struct ocfs2_group_desc *) bh2jh(bg_bh)->b_committed_data;
+ jh = bh2jh(bg_bh);
+ spin_lock(&jh->b_state_lock);
+ bg = (struct ocfs2_group_desc *) jh->b_committed_data;
if (bg)
ret = !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
else
ret = 1;
- jbd_unlock_bh_state(bg_bh);
+ spin_unlock(&jh->b_state_lock);
return ret;
}
@@ -2387,6 +2389,7 @@ static int ocfs2_block_group_clear_bits(handle_t *handle,
int status;
unsigned int tmp;
struct ocfs2_group_desc *undo_bg = NULL;
+ struct journal_head *jh;
/* The caller got this descriptor from
* ocfs2_read_group_descriptor(). Any corruption is a code bug. */
@@ -2405,10 +2408,10 @@ static int ocfs2_block_group_clear_bits(handle_t *handle,
goto bail;
}
+ jh = bh2jh(group_bh);
if (undo_fn) {
- jbd_lock_bh_state(group_bh);
- undo_bg = (struct ocfs2_group_desc *)
- bh2jh(group_bh)->b_committed_data;
+ spin_lock(&jh->b_state_lock);
+ undo_bg = (struct ocfs2_group_desc *) jh->b_committed_data;
BUG_ON(!undo_bg);
}
@@ -2423,7 +2426,7 @@ static int ocfs2_block_group_clear_bits(handle_t *handle,
le16_add_cpu(&bg->bg_free_bits_count, num_bits);
if (le16_to_cpu(bg->bg_free_bits_count) > le16_to_cpu(bg->bg_bits)) {
if (undo_fn)
- jbd_unlock_bh_state(group_bh);
+ spin_unlock(&jh->b_state_lock);
return ocfs2_error(alloc_inode->i_sb, "Group descriptor # %llu has bit count %u but claims %u are freed. num_bits %d\n",
(unsigned long long)le64_to_cpu(bg->bg_blkno),
le16_to_cpu(bg->bg_bits),
@@ -2432,7 +2435,7 @@ static int ocfs2_block_group_clear_bits(handle_t *handle,
}
if (undo_fn)
- jbd_unlock_bh_state(group_bh);
+ spin_unlock(&jh->b_state_lock);
ocfs2_journal_dirty(handle, group_bh);
bail: