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authorDavid Howells <dhowells@redhat.com>2006-06-23 05:02:57 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-23 10:42:45 -0400
commit454e2398be9b9fa30433fccc548db34d19aa9958 (patch)
tree1f61cb0c3716a33b661cfc8977e9beeb480a322c /arch
parent1ad5544098a69d7dc1fa508cbb17e13a7a952fd8 (diff)
[PATCH] VFS: Permit filesystem to override root dentry on mount
Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/ia64/kernel/perfmon.c7
-rw-r--r--arch/powerpc/platforms/cell/spufs/inode.c6
2 files changed, 7 insertions, 6 deletions
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 077f21216b65..2359e2809f50 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -595,10 +595,11 @@ pfm_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
595} 595}
596 596
597 597
598static struct super_block * 598static int
599pfmfs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) 599pfmfs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data,
600 struct vfsmount *mnt)
600{ 601{
601 return get_sb_pseudo(fs_type, "pfm:", NULL, PFMFS_MAGIC); 602 return get_sb_pseudo(fs_type, "pfm:", NULL, PFMFS_MAGIC, mnt);
602} 603}
603 604
604static struct file_system_type pfm_fs_type = { 605static struct file_system_type pfm_fs_type = {
diff --git a/arch/powerpc/platforms/cell/spufs/inode.c b/arch/powerpc/platforms/cell/spufs/inode.c
index 1987697b23a0..7b4572805db9 100644
--- a/arch/powerpc/platforms/cell/spufs/inode.c
+++ b/arch/powerpc/platforms/cell/spufs/inode.c
@@ -436,11 +436,11 @@ spufs_fill_super(struct super_block *sb, void *data, int silent)
436 return spufs_create_root(sb, data); 436 return spufs_create_root(sb, data);
437} 437}
438 438
439static struct super_block * 439static int
440spufs_get_sb(struct file_system_type *fstype, int flags, 440spufs_get_sb(struct file_system_type *fstype, int flags,
441 const char *name, void *data) 441 const char *name, void *data, struct vfsmount *mnt)
442{ 442{
443 return get_sb_single(fstype, flags, data, spufs_fill_super); 443 return get_sb_single(fstype, flags, data, spufs_fill_super, mnt);
444} 444}
445 445
446static struct file_system_type spufs_type = { 446static struct file_system_type spufs_type = {