kato f067b60f38 Clustered read and write are switched at mount-option level. ... 1. Clustered I/O is switched by the MNT_NOCLUSTERR and MNT_NOCLUSTERW bits of the mnt_flag. The sysctl variables, vfs.foo.doclusterread and vfs.foo.doclusterwrite are deleted. Only mount option can control clustered I/O from userland. 2. When foofs_mount mounts block device, foofs_mount checks D_CLUSTERR and D_CLUSTERW bits of the d_flags member in the block device switch table. If D_NOCLUSTERR / D_NOCLUSTERW are set, MNT_NOCLUSTERR / MNT_NOCLUSTERW bits will be set. In this case, MNT_NOCLUSTERR and MNT_NOCLUSTERW cannot be cleared from userland. 3. Vnode driver disables both clustered read and write. 4. Union filesystem disables clutered write. Reviewed by: bde		1997-09-27 13:40:20 +00:00
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spec_vnops.c	Clustered read and write are switched at mount-option level.	1997-09-27 13:40:20 +00:00