[XFS] Introduce two new mount options (nolargeio/largeio) to allow
filesystems to expose the filesystem stripe width in stat(2) rather than
the page cache size. This allows applications requiring high bandwidth to
easily determine the optimum I/O size for the underlying filesystem. The
default is to report the page cache size (i.e. "nolargeio").
SGI-PV: 942818
SGI-Modid: xfs-linux:xfs-kern:23830a
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 0653bee..b71af18 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -421,6 +421,9 @@
* allocation */
#define XFS_MOUNT_IHASHSIZE 0x00100000 /* inode hash table size */
#define XFS_MOUNT_DIRSYNC 0x00200000 /* synchronous directory ops */
+#define XFS_MOUNT_COMPAT_IOSIZE 0x00400000 /* don't report large preferred
+ * I/O size in stat() */
+
/*
* Default minimum read and write sizes.
@@ -442,6 +445,30 @@
#define XFS_WSYNC_READIO_LOG 15 /* 32K */
#define XFS_WSYNC_WRITEIO_LOG 14 /* 16K */
+/*
+ * Allow large block sizes to be reported to userspace programs if the
+ * "largeio" mount option is used.
+ *
+ * If compatibility mode is specified, simply return the basic unit of caching
+ * so that we don't get inefficient read/modify/write I/O from user apps.
+ * Otherwise....
+ *
+ * If the underlying volume is a stripe, then return the stripe width in bytes
+ * as the recommended I/O size. It is not a stripe and we've set a default
+ * buffered I/O size, return that, otherwise return the compat default.
+ */
+static inline unsigned long
+xfs_preferred_iosize(xfs_mount_t *mp)
+{
+ if (mp->m_flags & XFS_MOUNT_COMPAT_IOSIZE)
+ return PAGE_CACHE_SIZE;
+ return (mp->m_swidth ?
+ (mp->m_swidth << mp->m_sb.sb_blocklog) :
+ ((mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) ?
+ (1 << (int)MAX(mp->m_readio_log, mp->m_writeio_log)) :
+ PAGE_CACHE_SIZE));
+}
+
#define XFS_MAXIOFFSET(mp) ((mp)->m_maxioffset)
#define XFS_FORCED_SHUTDOWN(mp) ((mp)->m_flags & XFS_MOUNT_FS_SHUTDOWN)