From: Viacheslav Dubeyko <slava@dubeyko.com>
To: ceph-devel@vger.kernel.org
Cc: idryomov@gmail.com, linux-fsdevel@vger.kernel.org,
pdonnell@redhat.com, amarkuze@redhat.com, Slava.Dubeyko@ibm.com,
slava@dubeyko.com
Subject: [PATCH] ceph: fix potentail race condition of operations with CEPH_I_ODIRECT flag
Date: Mon, 14 Jul 2025 14:47:19 -0700 [thread overview]
Message-ID: <20250714214719.589469-1-slava@dubeyko.com> (raw)
From: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
The Coverity Scan service has detected potential
race conditions in ceph_block_o_direct(), ceph_start_io_read(),
ceph_block_buffered(), and ceph_start_io_direct() [1 - 4].
The CID 1590942, 1590665, 1589664, 1590377 contain explanation:
"The value of the shared data will be determined by
the interleaving of thread execution. Thread shared data is accessed
without holding an appropriate lock, possibly causing
a race condition (CWE-366)".
This patch reworks the pattern of accessing/modification of
CEPH_I_ODIRECT flag by means of adding smp_mb__before_atomic()
before reading the status of CEPH_I_ODIRECT flag and
smp_mb__after_atomic() after clearing set/clear this flag.
Also, it was reworked the pattern of using of ci->i_ceph_lock
in ceph_block_o_direct(), ceph_start_io_read(),
ceph_block_buffered(), and ceph_start_io_direct() methods.
[1] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1590942
[2] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1590665
[3] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1589664
[4] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1590377
Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
cc: Alex Markuze <amarkuze@redhat.com>
cc: Ilya Dryomov <idryomov@gmail.com>
cc: Ceph Development <ceph-devel@vger.kernel.org>
---
fs/ceph/io.c | 53 +++++++++++++++++++++++++++++++++++++++----------
fs/ceph/super.h | 3 ++-
2 files changed, 44 insertions(+), 12 deletions(-)
diff --git a/fs/ceph/io.c b/fs/ceph/io.c
index c456509b31c3..91b73052d708 100644
--- a/fs/ceph/io.c
+++ b/fs/ceph/io.c
@@ -21,14 +21,23 @@
/* Call with exclusively locked inode->i_rwsem */
static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode)
{
+ bool is_odirect;
+
lockdep_assert_held_write(&inode->i_rwsem);
- if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) {
- spin_lock(&ci->i_ceph_lock);
- ci->i_ceph_flags &= ~CEPH_I_ODIRECT;
- spin_unlock(&ci->i_ceph_lock);
- inode_dio_wait(inode);
+ spin_lock(&ci->i_ceph_lock);
+ /* ensure that bit state is consistent */
+ smp_mb__before_atomic();
+ is_odirect = READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT;
+ if (is_odirect) {
+ clear_bit(CEPH_I_ODIRECT_BIT, &ci->i_ceph_flags);
+ /* ensure modified bit is visible */
+ smp_mb__after_atomic();
}
+ spin_unlock(&ci->i_ceph_lock);
+
+ if (is_odirect)
+ inode_dio_wait(inode);
}
/**
@@ -51,10 +60,16 @@ void
ceph_start_io_read(struct inode *inode)
{
struct ceph_inode_info *ci = ceph_inode(inode);
+ bool is_odirect;
/* Be an optimist! */
down_read(&inode->i_rwsem);
- if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT))
+ spin_lock(&ci->i_ceph_lock);
+ /* ensure that bit state is consistent */
+ smp_mb__before_atomic();
+ is_odirect = READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT;
+ spin_unlock(&ci->i_ceph_lock);
+ if (!is_odirect)
return;
up_read(&inode->i_rwsem);
/* Slow path.... */
@@ -106,12 +121,22 @@ ceph_end_io_write(struct inode *inode)
/* Call with exclusively locked inode->i_rwsem */
static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode)
{
+ bool is_odirect;
+
lockdep_assert_held_write(&inode->i_rwsem);
- if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) {
- spin_lock(&ci->i_ceph_lock);
- ci->i_ceph_flags |= CEPH_I_ODIRECT;
- spin_unlock(&ci->i_ceph_lock);
+ spin_lock(&ci->i_ceph_lock);
+ /* ensure that bit state is consistent */
+ smp_mb__before_atomic();
+ is_odirect = READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT;
+ if (!is_odirect) {
+ set_bit(CEPH_I_ODIRECT_BIT, &ci->i_ceph_flags);
+ /* ensure modified bit is visible */
+ smp_mb__after_atomic();
+ }
+ spin_unlock(&ci->i_ceph_lock);
+
+ if (!is_odirect) {
/* FIXME: unmap_mapping_range? */
filemap_write_and_wait(inode->i_mapping);
}
@@ -137,10 +162,16 @@ void
ceph_start_io_direct(struct inode *inode)
{
struct ceph_inode_info *ci = ceph_inode(inode);
+ bool is_odirect;
/* Be an optimist! */
down_read(&inode->i_rwsem);
- if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)
+ spin_lock(&ci->i_ceph_lock);
+ /* ensure that bit state is consistent */
+ smp_mb__before_atomic();
+ is_odirect = READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT;
+ spin_unlock(&ci->i_ceph_lock);
+ if (is_odirect)
return;
up_read(&inode->i_rwsem);
/* Slow path.... */
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index bb0db0cc8003..969212637c5b 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -638,7 +638,8 @@ static inline struct inode *ceph_find_inode(struct super_block *sb,
#define CEPH_I_FLUSH_SNAPS (1 << 8) /* need flush snapss */
#define CEPH_I_ERROR_WRITE (1 << 9) /* have seen write errors */
#define CEPH_I_ERROR_FILELOCK (1 << 10) /* have seen file lock errors */
-#define CEPH_I_ODIRECT (1 << 11) /* inode in direct I/O mode */
+#define CEPH_I_ODIRECT_BIT (11) /* inode in direct I/O mode */
+#define CEPH_I_ODIRECT (1 << CEPH_I_ODIRECT_BIT)
#define CEPH_ASYNC_CREATE_BIT (12) /* async create in flight for this */
#define CEPH_I_ASYNC_CREATE (1 << CEPH_ASYNC_CREATE_BIT)
#define CEPH_I_SHUTDOWN (1 << 13) /* inode is no longer usable */
--
2.49.0
reply other threads:[~2025-07-14 21:47 UTC|newest]
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