[PATCH] cifs: Add information about noserverino

[Bernhard Walle <bernhard@bwalle.de>]

In my case I had the problem that 32 bit userspace applications in an
amd64 environment was not able to list the directories of a CIFS-mounted
share. The simple userspace code

    int main(int argc, char *argv[])
    {
        DIR *dir;
        struct dirent *dirent;

        if (!argv[1]) {
            fprintf(stderr, "Usage: %s <directory>\n", argv[0]);
            return -1;
        }

        dir = opendir(argv[1]);
        if (!dir) {
            perror("Unable to open directory");
            return -1;
        }

        while ((dirent = readdir(dir)) != NULL)
            puts(dirent->d_name);

        closedir(dir);

        return 0;
    }

was sufficient to trigger the problem.

I discovered that the problem was that the inodes were too large to fit
in a 32 bit (unsigned long) integer, so the compat_filldir() function
returned -EOVERFLOW.

While that is okay it would have saved me a some hours of debugging if
the message below would have appeared in my kernel log.

The target was a Samba server (I guess) of a Buffalo LinkStation Duo
with the unmodified vendor firmware 1.34.

Signed-off-by: Bernhard Walle <bernhard@bwalle.de>
---
 fs/cifs/readdir.c |   23 +++++++++++++++++++----
 1 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index d5e591f..d979826 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -773,6 +773,7 @@ int cifs_readdir(struct file *file, void *direntry, filldir_t filldir)
 	char *tmp_buf = NULL;
 	char *end_of_smb;
 	unsigned int max_len;
+	int err;
 
 	xid = GetXid();
 
@@ -783,17 +784,31 @@ int cifs_readdir(struct file *file, void *direntry, filldir_t filldir)
 
 	switch ((int) file->f_pos) {
 	case 0:
-		if (filldir(direntry, ".", 1, file->f_pos,
-		     file->f_path.dentry->d_inode->i_ino, DT_DIR) < 0) {
+		err = filldir(direntry, ".", 1, file->f_pos,
+		     file->f_path.dentry->d_inode->i_ino, DT_DIR);
+		if (err < 0) {
 			cERROR(1, "Filldir for current dir failed");
+			if (err == -EOVERFLOW) {
+				cERROR(1, "Server inodes are too large for 32 "
+						"bit userspace. You might "
+						"consider using 'noserverino' "
+						"mount option for this mount.");
+			}
 			rc = -ENOMEM;
 			break;
 		}
 		file->f_pos++;
 	case 1:
-		if (filldir(direntry, "..", 2, file->f_pos,
-		     file->f_path.dentry->d_parent->d_inode->i_ino, DT_DIR) < 0) {
+		err = filldir(direntry, "..", 2, file->f_pos,
+		     file->f_path.dentry->d_parent->d_inode->i_ino, DT_DIR);
+		if (err < 0) {
 			cERROR(1, "Filldir for parent dir failed");
+			if (err == -EOVERFLOW) {
+				cERROR(1, "Server inodes are too large for 32 "
+						"bit userspace. You might "
+						"consider using 'noserverino' "
+						"mount option for this mount.");
+			}
 			rc = -ENOMEM;
 			break;
 		}
-- 
1.7.3.2