Commit a3a065e3f13da8a3470ed09c7f38aad256083726 changes the behavior
of dentry for pipe, sockets and anon_inodes (eventfd, timerfd, epoll,
signalfd and perf...):
"""
Filesystems outside the regular namespace do not have to clear
in order to have a working /proc/$pid/fd/XXX. Nothing in proc prevents the
fd link from being used if its dentry is not in the hash.
Also, it does not get put into the dcache hash if DCACHE_UNHASHED is clear;
that depends on the filesystem calling d_add or d_rehash.
So delete the misleading comments and needless code.
"""
That made checkpoint complain on half-closed pipes which are
DCACHE_UNHASHED and trigger the d_unlinked() test.
This patch proposes one fix - which is to mark such dentry with a
special flag DCACHE_SPECIAL_INODE, which indicates that this dentry
is an exception, and the d_unlinked() doesn't matter.
An alternative approach would be to add an unlinked() method to file
operations: if it's null, then checkpoint will test with d_unlinked()
otherwise it will test with the specific method. for these filesystems
we'll make this method return "ok" always. This may also be useful if
unlinking a file becomes a per-filesystem operation.
Comments ?
Oren.
---
checkpoint/files.c | 2 +-
fs/anon_inodes.c | 1 +
fs/pipe.c | 1 +
include/linux/dcache.h | 14 +++++++++++++-
net/socket.c | 1 +
5 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/checkpoint/files.c b/checkpoint/files.c
index d1242f2..fa318f3 100644
--- a/checkpoint/files.c
+++ b/checkpoint/files.c
@@ -231,7 +231,7 @@ int checkpoint_file(struct ckpt_ctx *ctx, void *ptr)
file, file->f_op);
return -EBADF;
}
- if (d_unlinked(file->f_dentry)) {
+ if (!d_special_inode(file->f_dentry) && d_unlinked(file->f_dentry)) {
ckpt_err(ctx, -EBADF, "%(T)%(P)Unlinked files unsupported\n",
file);
return -EBADF;
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 9f0bf13..a7bf417 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -118,6 +118,7 @@ struct file *anon_inode_getfile(const char *name,
atomic_inc(&anon_inode_inode->i_count);
path.dentry->d_op = &anon_inodefs_dentry_operations;
+ path.dentry->d_flags |= DCACHE_SPECIAL_INODE;
d_instantiate(path.dentry, anon_inode_inode);
error = -ENFILE;
diff --git a/fs/pipe.c b/fs/pipe.c
index 8c79493..2fd5ad6 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1213,6 +1213,7 @@ struct file *create_write_pipe(int flags)
path.mnt = mntget(pipe_mnt);
path.dentry->d_op = &pipefs_dentry_operations;
+ path.dentry->d_flags |= DCACHE_SPECIAL_INODE;
d_instantiate(path.dentry, inode);
err = -ENFILE;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 30b93b2..af01318 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -186,6 +186,13 @@ d_iput: no no no yes
#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */
+#define DCACHE_SPECIAL_INODE 0x0100
+ /* This dentry corresponds to a special inode, like anon-inode,
+ * pipe, and sockets. It is set once by the file-system. Used by
+ * checkpoint/restart to ignore a positive d_unlinked() for such
+ * dentries (a closed pipe is not a unlinked file)
+ */
+
extern spinlock_t dcache_lock;
extern seqlock_t rename_lock;
@@ -347,7 +354,12 @@ extern struct dentry * dget_locked(struct dentry *);
*
* Returns true if the dentry passed is not currently hashed.
*/
-
+
+static inline int d_special_inode(struct dentry *dentry)
+{
+ return (dentry->d_flags & DCACHE_SPECIAL_INODE);
+}
+
static inline int d_unhashed(struct dentry *dentry)
{
return (dentry->d_flags & DCACHE_UNHASHED);
diff --git a/net/socket.c b/net/socket.c
index 3253c04..dd5983a 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -365,6 +365,7 @@ int sock_alloc_file(struct socket *sock, struct file **f, int flags)
path.mnt = mntget(sock_mnt);
path.dentry->d_op = &sockfs_dentry_operations;
+ path.dentry->d_flags |= DCACHE_SPECIAL_INODE;
d_instantiate(path.dentry, SOCK_INODE(sock));
SOCK_INODE(sock)->i_fop = &socket_file_ops;
--
1.6.3.3
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