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xfs: exclude never-released buffers from buftarg I/O accounting 

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@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Brian Foster 2016-07-20 11:13:43 +10:00 committed by Dave Chinner
parent 5539d36752
commit c891c30a4d
4 changed files with 12 additions and 7 deletions
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3
fs/xfs/xfs_buf.c
View File

@ -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;

1
fs/xfs/xfs_buf.h
View File

@ -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 */

5
fs/xfs/xfs_log.c
View File

@ -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;

10
fs/xfs/xfs_mount.c
View File

@ -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);