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From: Andreas Gruenbacher <agruenba@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
	cluster-devel@redhat.com, linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.cz>,
	Matthew Wilcox <willy@infradead.org>
Subject: [RFC 7/9] gfs2: Encode glock holding and retry flags in journal_info
Date: Mon, 31 May 2021 19:01:21 +0200	[thread overview]
Message-ID: <20210531170123.243771-8-agruenba@redhat.com> (raw)
In-Reply-To: <20210531170123.243771-1-agruenba@redhat.com>

Use the lowest two bits in current->journal_info to encode when
we're holding a glock, and when an operation holding a glock
needs to be retried.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/incore.h | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index aa8d1a23132d..e32433df119c 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -871,14 +871,45 @@ static inline unsigned gfs2_max_stuffed_size(const struct gfs2_inode *ip)
 	return GFS2_SB(&ip->i_inode)->sd_sb.sb_bsize - sizeof(struct gfs2_dinode);
 }
 
+/*
+ * Transactions are always memory aligned, so we use bit 0 of
+ * current->journal_info to indicate when we're holding a glock and so taking
+ * random additional glocks might deadlock, and bit 1 to indicate when such an
+ * operation needs to be retried after dropping and re-acquiring that "outer"
+ * glock.
+ */
+
 static inline struct gfs2_trans *current_trans(void)
 {
-	return current->journal_info;
+	return (void *)((long)current->journal_info & ~3);
 }
 
 static inline void set_current_trans(struct gfs2_trans *tr)
 {
-	current->journal_info = tr;
+	long flags = (long)current->journal_info & 3;
+	current->journal_info = (void *)((long)tr | flags);
+}
+
+static inline bool current_holds_glock(void)
+{
+	return (long)current->journal_info & 1;
+}
+
+static inline bool current_needs_retry(void)
+{
+	return (long)current->journal_info & 2;
+}
+
+static inline void set_current_holds_glock(bool b)
+{
+	current->journal_info =
+		(void *)(((long)current->journal_info & ~1) | b);
+}
+
+static inline void set_current_needs_retry(bool b)
+{
+	current->journal_info =
+		(void *)(((long)current->journal_info & ~2) | (b << 1));
 }
 
 #endif /* __INCORE_DOT_H__ */
-- 
2.26.3


  parent reply	other threads:[~2021-05-31 17:10 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-31 17:01 [RFC 0/9] gfs2: handle page faults during read and write Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 1/9] gfs2: Clean up the error handling in gfs2_page_mkwrite Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 2/9] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 3/9] gfs2: Add gfs2_holder_is_compatible helper Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 4/9] gfs2: Fix mmap + page fault deadlocks (part 1) Andreas Gruenbacher
2021-06-01  6:00   ` Linus Torvalds
2021-06-02 11:16     ` Andreas Gruenbacher
2021-06-11 16:25       ` Al Viro
2021-06-12 21:05         ` Al Viro
2021-06-12 21:35           ` Al Viro
2021-06-13  8:44             ` [Cluster-devel] " Steven Whitehouse
2021-05-31 17:01 ` [RFC 5/9] iov_iter: Add iov_iter_fault_in_writeable() Andreas Gruenbacher
2021-05-31 17:12   ` Al Viro
2021-06-12 21:12     ` Al Viro
2021-06-12 21:33       ` Linus Torvalds
2021-06-12 21:47         ` Al Viro
2021-06-12 23:17           ` Linus Torvalds
2021-06-12 23:38             ` Al Viro
2021-05-31 17:01 ` [RFC 6/9] gfs2: Add wrappers for accessing journal_info Andreas Gruenbacher
2021-05-31 17:01 ` Andreas Gruenbacher [this message]
2021-05-31 17:01 ` [RFC 8/9] gfs2: Add LM_FLAG_OUTER glock holder flag Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 9/9] gfs2: Fix mmap + page fault deadlocks (part 2) Andreas Gruenbacher
2021-06-01  5:47   ` Linus Torvalds
     [not found] ` <CAHk-=wgX=fZ+y=SxBsod8CvZmZ0-X7vZ6dV6EgLPkpBXbt=nQQ@mail.gmail.com>
2021-05-31 20:35   ` [RFC 0/9] gfs2: handle page faults during read and write Andreas Gruenbacher

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