Created attachment 1586648 [details]
windows error dialogue box

Description of problem:
Windows client errors out while copying large file into GlusterFS volume share configured with fruit and streams_xattr VFS modules. See attachment for error message.

Version-Release number of selected component (if applicable):
master

How reproducible:
Always

Steps to Reproduce:
1. Create a basic distribute-replicate volume
2. Enable "group samba" volume set on the volume
3. Set up a Samba share with fruit and streams_xattr VFS modules
   vfs objects = fruit streams_xattr glusterfs
4. Connect to the share from a Windows client
5. Try to copy a large file(probably with size > 600M) into share

Actual results:
Windows client fails to copy large file with error(see attachment).

Expected results:
Copy completes successfully.

Additional info(root cause):
Problem lies in md-cache layer where it fails to update cache for xattrs with null value("\0"). Following steps reproduce the core issue on a plain FUSE mount:

# touch /mnt/glusterfs/foobar

# setfattr -n "user.DosStream.Zone.Identifier:\$DATA" -v "\0"
/mnt/glusterfs/foobar 

# echo $?
0

# getfattr -d -m . -e hex /mnt/glusterfs/foobar 
getfattr: Removing leading '/' from absolute path names
# file: mnt/glusterfs/foobar
security.selinux=0x73797374656d5f753a6f626a6563745f723a6675736566735f74
3a733000
/mnt/glusterfs/foobar: user.DosStream.Zone.Identifier:$DATA: No such
attribute

# getfattr -d -m . -e hex /brick/brick1/foobar 
getfattr: Removing leading '/' from absolute path names
# file: brick/brick1/foobar
security.selinux=0x73797374656d5f753a6f626a6563745f723a676c757374657264
5f627269636b5f743a733000
trusted.gfid=0xde7d450691b24107b0c03fac58d9e49e
trusted.gfid2path.17f514a2c19aaa57=0x30303030303030302d303030302d303030
302d303030302d3030303030303030303030312f666f6f626172
user.DosStream.Zone.Identifier:$DATA=0x00

# gluster v set vol performance.cache-samba-metadata off
volume set: success

# getfattr -d -m . -e hex /mnt/glusterfs/foobar 
getfattr: Removing leading '/' from absolute path names
# file: mnt/glusterfs/foobar
security.selinux=0x73797374656d5f753a6f626a6563745f723a6675736566735f74
3a733000
user.DosStream.Zone.Identifier:$DATA=0x00