The upcoming buftarg I/O accounting mechanism maintains a count of all
buffers that have undergone I/O in the current hold-release cycle.
Certain buffers associated with core infrastructure (e.g., the xfs_mount
superblock buffer, log buffers) are never released, however. This means
that accounting I/O submission on such buffers elevates the buftarg
count indefinitely and could lead to lockup on unmount.
Define a new buffer flag to explicitly exclude buffers from buftarg I/O
accounting. Set the flag on the superblock and associated log buffers.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
---
fs/xfs/xfs_buf.c | 3 ++-
fs/xfs/xfs_buf.h | 1 +
fs/xfs/xfs_log.c | 5 +++--
fs/xfs/xfs_mount.c | 10 ++++++----
4 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 4665ff6..12f7bec 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -815,7 +815,8 @@ xfs_buf_get_uncached(
struct xfs_buf *bp;
DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
- bp = _xfs_buf_alloc(target, &map, 1, 0);
+ /* flags might contain irrelevant bits, pass only what we care about */
+ bp = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT);
if (unlikely(bp == NULL))
goto fail;
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 8bfb974..e2108da 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -43,6 +43,7 @@ typedef enum {
#define XBF_READ (1 << 0) /* buffer intended for reading from device */
#define XBF_WRITE (1 << 1) /* buffer intended for writing to device */
#define XBF_READ_AHEAD (1 << 2) /* asynchronous read-ahead */
+#define XBF_NO_IOACCT (1 << 3) /* bypass I/O accounting (non-LRU bufs) */
#define XBF_ASYNC (1 << 4) /* initiator will not wait for completion */
#define XBF_DONE (1 << 5) /* all pages in the buffer uptodate */
#define XBF_STALE (1 << 6) /* buffer has been staled, do not find it */
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 63dad9e..3b74fa0 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1415,7 +1415,7 @@ xlog_alloc_log(
*/
error = -ENOMEM;
bp = xfs_buf_alloc(mp->m_logdev_targp, XFS_BUF_DADDR_NULL,
- BTOBB(log->l_iclog_size), 0);
+ BTOBB(log->l_iclog_size), XBF_NO_IOACCT);
if (!bp)
goto out_free_log;
@@ -1454,7 +1454,8 @@ xlog_alloc_log(
prev_iclog = iclog;
bp = xfs_buf_get_uncached(mp->m_logdev_targp,
- BTOBB(log->l_iclog_size), 0);
+ BTOBB(log->l_iclog_size),
+ XBF_NO_IOACCT);
if (!bp)
goto out_free_iclog;
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index e39b023..970c19b 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -272,13 +272,15 @@ xfs_readsb(
buf_ops = NULL;
/*
- * Allocate a (locked) buffer to hold the superblock.
- * This will be kept around at all times to optimize
- * access to the superblock.
+ * Allocate a (locked) buffer to hold the superblock. This will be kept
+ * around at all times to optimize access to the superblock. Therefore,
+ * set XBF_NO_IOACCT to make sure it doesn't hold the buftarg count
+ * elevated.
*/
reread:
error = xfs_buf_read_uncached(mp->m_ddev_targp, XFS_SB_DADDR,
- BTOBB(sector_size), 0, &bp, buf_ops);
+ BTOBB(sector_size), XBF_NO_IOACCT, &bp,
+ buf_ops);
if (error) {
if (loud)
xfs_warn(mp, "SB validate failed with error %d.", error);
--
2.5.5
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