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authorNick Piggin <npiggin@kernel.dk>2011-01-07 17:49:54 +1100
committerNick Piggin <npiggin@kernel.dk>2011-01-07 17:50:28 +1100
commit5f57cbcc02cf18f6b22ef4066bb10afeb8f930ff (patch)
treef02e7ee57e6060f0af1bcda281baf2972d2da72f /include
parentc28cc36469554dc55540f059fbdc7fa22a2c31fc (diff)
fs: dcache remove d_mounted
Rather than keep a d_mounted count in the dentry, set a dentry flag instead. The flag can be cleared by checking the hash table to see if there are any mounts left, which is not time critical because it is performed at detach time. The mounted state of a dentry is only used to speculatively take a look in the mount hash table if it is set -- before following the mount, vfsmount lock is taken and mount re-checked without races. This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole I might use later (and some configs have larger than 32-bit spinlocks which might make use of the hole). Autofs4 conversion and changelog by Ian Kent <raven@themaw.net>: In autofs4, when expring direct (or offset) mounts we need to ensure that we block user path walks into the autofs mount, which is covered by another mount. To do this we clear the mounted status so that follows stop before walking into the mount and are essentially blocked until the expire is completed. The automount daemon still finds the correct dentry for the umount due to the follow mount logic in fs/autofs4/root.c:autofs4_follow_link(), which is set as an inode operation for direct and offset mounts only and is called following the lookup that stopped at the covered mount. At the end of the expire the covering mount probably has gone away so the mounted status need not be restored. But we need to check this and only restore the mounted status if the expire failed. XXX: autofs may not work right if we have other mounts go over the top of it? Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Diffstat (limited to 'include')
-rw-r--r--include/linux/dcache.h42
1 files changed, 21 insertions, 21 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c2e7390289c..e4414693065 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -92,7 +92,6 @@ struct dentry {
unsigned int d_flags; /* protected by d_lock */
spinlock_t d_lock; /* per dentry lock */
seqcount_t d_seq; /* per dentry seqlock */
- int d_mounted;
struct inode *d_inode; /* Where the name belongs to - NULL is
* negative */
/*
@@ -156,33 +155,34 @@ struct dentry_operations {
/* d_flags entries */
#define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
-#define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
- * renamed" and has to be
- * deleted on the last dput()
- */
-#define DCACHE_DISCONNECTED 0x0004
- /* This dentry is possibly not currently connected to the dcache tree,
- * in which case its parent will either be itself, or will have this
- * flag as well. nfsd will not use a dentry with this bit set, but will
- * first endeavour to clear the bit either by discovering that it is
- * connected, or by performing lookup operations. Any filesystem which
- * supports nfsd_operations MUST have a lookup function which, if it finds
- * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
- * that dentry into place and return that dentry rather than the passed one,
- * typically using d_splice_alias.
- */
+#define DCACHE_NFSFS_RENAMED 0x0002
+ /* this dentry has been "silly renamed" and has to be deleted on the last
+ * dput() */
+
+#define DCACHE_DISCONNECTED 0x0004
+ /* This dentry is possibly not currently connected to the dcache tree, in
+ * which case its parent will either be itself, or will have this flag as
+ * well. nfsd will not use a dentry with this bit set, but will first
+ * endeavour to clear the bit either by discovering that it is connected,
+ * or by performing lookup operations. Any filesystem which supports
+ * nfsd_operations MUST have a lookup function which, if it finds a
+ * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
+ * dentry into place and return that dentry rather than the passed one,
+ * typically using d_splice_alias. */
#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
#define DCACHE_UNHASHED 0x0010
-
-#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched by inotify */
+#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
+ /* Parent inode is watched by inotify */
#define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
-
-#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */
+#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
+ /* Parent inode is watched by some fsnotify listener */
#define DCACHE_CANT_MOUNT 0x0100
#define DCACHE_GENOCIDE 0x0200
+#define DCACHE_MOUNTED 0x0400 /* is a mountpoint */
+
extern spinlock_t dcache_inode_lock;
extern seqlock_t rename_lock;
@@ -372,7 +372,7 @@ extern void dput(struct dentry *);
static inline int d_mountpoint(struct dentry *dentry)
{
- return dentry->d_mounted;
+ return dentry->d_flags & DCACHE_MOUNTED;
}
extern struct vfsmount *lookup_mnt(struct path *);