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author | Thomas Gleixner <tglx@linutronix.de> | 2019-08-09 14:42:32 +0200 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2019-10-21 09:16:46 -0400 |
commit | 464170647b5648bb81f3615567485fcb9a685bed (patch) | |
tree | cb8bee9bf114c269de6c405bdb0fcdafbd65dd76 /fs/ocfs2/suballoc.c | |
parent | 2e710ff03fc4599059eeda68c8de2383e65af825 (diff) | |
download | linux-464170647b5648bb81f3615567485fcb9a685bed.tar.gz linux-464170647b5648bb81f3615567485fcb9a685bed.tar.bz2 linux-464170647b5648bb81f3615567485fcb9a685bed.zip |
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/suballoc.c')
-rw-r--r-- | fs/ocfs2/suballoc.c | 19 |
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: |