[readdir] introduce ->iterate(), ctx->pos, dir_emit()

New method - ->iterate(file, ctx).  That's the replacement for ->readdir();
it takes callback from ctx->actor, uses ctx->pos instead of file->f_pos and
calls dir_emit(ctx, ...) instead of filldir(data, ...).  It does *not*
update file->f_pos (or look at it, for that matter); iterate_dir() does the
update.

Note that dir_emit() takes the offset from ctx->pos (and eventually
filldir_t will lose that argument).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

7 files changed, 47 insertions, 18 deletions

diff --git a/arch/parisc/hpux/fs.c b/arch/parisc/hpux/fs.c
index fc2cbee86e34..eca8230267cc 100644
--- a/arch/parisc/hpux/fs.c
+++ b/arch/parisc/hpux/fs.c
@@ -129,7 +129,7 @@ int hpux_getdents(unsigned int fd, struct hpux_dirent __user *dirent, unsigned i
                 error = buf.error;
         lastdirent = buf.previous;
         if (lastdirent) {
-                if (put_user(arg.file->f_pos, &lastdirent->d_off))
+                if (put_user(buf.ctx.pos, &lastdirent->d_off))
                         error = -EFAULT;
                 else
                         error = count - buf.count;
diff --git a/fs/coda/dir.c b/fs/coda/dir.c
index b7d3a05c062c..fc66861b3598 100644
--- a/fs/coda/dir.c
+++ b/fs/coda/dir.c
@@ -391,8 +391,7 @@ static int coda_readdir(struct file *coda_file, void *buf, filldir_t filldir)
         if (!host_file->f_op)
                 return -ENOTDIR;
 
-        if (host_file->f_op->readdir)
-        {
+        if (host_file->f_op->readdir) {
                 /* potemkin case: we were handed a directory inode.
                  * We can't use vfs_readdir because we have to keep the file
                  * position in sync between the coda_file and the host_file.
@@ -410,8 +409,20 @@ static int coda_readdir(struct file *coda_file, void *buf, filldir_t filldir)
 
                 coda_file->f_pos = host_file->f_pos;
                 mutex_unlock(&host_inode->i_mutex);
-        }
-        else /* Venus: we must read Venus dirents from a file */
+        } else if (host_file->f_op->iterate) {
+                struct inode *host_inode = file_inode(host_file);
+                struct dir_context *ctx = buf;
+
+                mutex_lock(&host_inode->i_mutex);
+                ret = -ENOENT;
+                if (!IS_DEADDIR(host_inode)) {
+                        ret = host_file->f_op->iterate(host_file, ctx);
+                        file_accessed(host_file);
+                }
+                mutex_unlock(&host_inode->i_mutex);
+
+                coda_file->f_pos = ctx->pos;
+        } else /* Venus: we must read Venus dirents from a file */
                 ret = coda_venus_readdir(coda_file, buf, filldir);
 
         return ret;
diff --git a/fs/compat.c b/fs/compat.c
index 2279b59e81f2..69ca1e301766 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -975,7 +975,7 @@ asmlinkage long compat_sys_getdents(unsigned int fd,
                 error = buf.error;
         lastdirent = buf.previous;
         if (lastdirent) {
-                if (put_user(f.file->f_pos, &lastdirent->d_off))
+                if (put_user(buf.ctx.pos, &lastdirent->d_off))
                         error = -EFAULT;
                 else
                         error = count - buf.count;
@@ -1062,7 +1062,7 @@ asmlinkage long compat_sys_getdents64(unsigned int fd,
                 error = buf.error;
         lastdirent = buf.previous;
         if (lastdirent) {
-                typeof(lastdirent->d_off) d_off = f.file->f_pos;
+                typeof(lastdirent->d_off) d_off = buf.ctx.pos;
                 if (__put_user_unaligned(d_off, &lastdirent->d_off))
                         error = -EFAULT;
                 else
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 7cb190426cec..6c8ef1dd4bdf 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -272,7 +272,7 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
                 goto out;
 
         error = -EINVAL;
-        if (!file->f_op->readdir)
+        if (!file->f_op->readdir && !file->f_op->iterate)
                 goto out_close;
 
         buffer.name = name;
diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 4f8cc6ba7c28..2fa2e2eb190b 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -240,11 +240,16 @@ struct name_list {
         struct list_head list;
 };
 
+struct nfs4_dir_ctx {
+        struct dir_context ctx;
+        struct list_head names;
+};
+
 static int
 nfsd4_build_namelist(void *arg, const char *name, int namlen,
                 loff_t offset, u64 ino, unsigned int d_type)
 {
-        struct list_head *names = arg;
+        struct nfs4_dir_ctx *ctx = arg;
         struct name_list *entry;
 
         if (namlen != HEXDIR_LEN - 1)
@@ -254,7 +259,7 @@ nfsd4_build_namelist(void *arg, const char *name, int namlen,
                 return -ENOMEM;
         memcpy(entry->name, name, HEXDIR_LEN - 1);
         entry->name[HEXDIR_LEN - 1] = '\0';
-        list_add(&entry->list, names);
+        list_add(&entry->list, &ctx->names);
         return 0;
 }
 
@@ -263,10 +268,7 @@ nfsd4_list_rec_dir(recdir_func *f, struct nfsd_net *nn)
 {
         const struct cred *original_cred;
         struct dentry *dir = nn->rec_file->f_path.dentry;
-        struct {
-                struct dir_context ctx;
-                struct list_head names;
-        } ctx;
+        struct nfs4_dir_ctx ctx;
         int status;
 
         status = nfs4_save_creds(&original_cred);
diff --git a/fs/readdir.c b/fs/readdir.c
index 5b620a2b45e6..5d6578affbbf 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -24,7 +24,7 @@ int iterate_dir(struct file *file, struct dir_context *ctx)
 {
         struct inode *inode = file_inode(file);
         int res = -ENOTDIR;
-        if (!file->f_op || !file->f_op->readdir)
+        if (!file->f_op || (!file->f_op->readdir && !file->f_op->iterate))
                 goto out;
 
         res = security_file_permission(file, MAY_READ);
@@ -37,7 +37,14 @@ int iterate_dir(struct file *file, struct dir_context *ctx)
 
         res = -ENOENT;
         if (!IS_DEADDIR(inode)) {
-                res = file->f_op->readdir(file, ctx, ctx->actor);
+                if (file->f_op->iterate) {
+                        ctx->pos = file->f_pos;
+                        res = file->f_op->iterate(file, ctx);
+                        file->f_pos = ctx->pos;
+                } else {
+                        res = file->f_op->readdir(file, ctx, ctx->actor);
+                        ctx->pos = file->f_pos;
+                }
                 file_accessed(file);
         }
         mutex_unlock(&inode->i_mutex);
@@ -214,7 +221,7 @@ SYSCALL_DEFINE3(getdents, unsigned int, fd,
                 error = buf.error;
         lastdirent = buf.previous;
         if (lastdirent) {
-                if (put_user(f.file->f_pos, &lastdirent->d_off))
+                if (put_user(buf.ctx.pos, &lastdirent->d_off))
                         error = -EFAULT;
                 else
                         error = count - buf.count;
@@ -296,7 +303,7 @@ SYSCALL_DEFINE3(getdents64, unsigned int, fd,
                 error = buf.error;
         lastdirent = buf.previous;
         if (lastdirent) {
-                typeof(lastdirent->d_off) d_off = f.file->f_pos;
+                typeof(lastdirent->d_off) d_off = buf.ctx.pos;
                 if (__put_user(d_off, &lastdirent->d_off))
                         error = -EFAULT;
                 else
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 643e5b6cbaf5..b9641ae68da8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1508,7 +1508,15 @@ int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
 typedef int (*filldir_t)(void *, const char *, int, loff_t, u64, unsigned);
 struct dir_context {
         filldir_t actor;
+        loff_t pos;
 };
+
+static inline bool dir_emit(struct dir_context *ctx,
+                            const char *name, int namelen,
+                            u64 ino, unsigned type)
+{
+        return ctx->actor(ctx, name, namelen, ctx->pos, ino, type) == 0;
+}
 struct block_device_operations;
 
 /* These macros are for out of kernel modules to test that
@@ -1525,6 +1533,7 @@ struct file_operations {
         ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
         ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
         int (*readdir) (struct file *, void *, filldir_t);
+        int (*iterate) (struct file *, struct dir_context *);
         unsigned int (*poll) (struct file *, struct poll_table_struct *);
         long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
         long (*compat_ioctl) (struct file *, unsigned int, unsigned long);