New: ext4 gives wrong errno with too long extended attribute values

http://bugzilla.kernel.org/show_bug.cgi?id=12793

Summary: ext4 gives wrong errno with too long extended attribute
values
Product: File System
Version: 2.5
KernelVersion: 2.6.29-rc6
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ext4
AssignedTo: [email protected]
ReportedBy: [email protected]

Latest working kernel version: haven't seen it working
Earliest failing kernel version: 2.6.28-gentoo-r1 had the same issue
Distribution: Gentoo
Hardware Environment: SMP Sun Mar 1 14:15:44 EET 2009 i686 Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz GenuineIntel GNU/Linux
Software Environment: Gentoo ~x86
Problem Description:

attr_set will fail if one or more of the following are true:

[ENOATTR] The attribute name given is not associated with the
indicated filesystem object and the ATTR_REPLACE flag bit was set.

[E2BIG] The value of the given attribute is too large, it
exceeds the maximum allowable size of an attribute value.

This is what the test script gives for ext4:

3900
4000
4100
Traceback (most recent call last):
File "test_xattr.py", line 10, in <module>

    xattr.set('/mnt/test/header.txt','user.test',s)                             

IOError: [Errno 28] No space left on device

This is what xfs gives:

65500
65600
Traceback (most recent call last):
File "test_xattr.py", line 10, in <module>

    xattr.set('/mnt/test/header.txt','user.test',s)

IOError: [Errno 7] Argument list too long

'E2BIG'

'ENOSPC'

Steps to reproduce:

betelgeuse@pena ~/python $ cat test_xattr.py
import xattr
hundred = ''
for i in range(100):

        hundred+='a'

s=hundred

while True:

        print len(s)
        xattr.set('/mnt/test/header.txt','user.test',s)
        s+=hundred

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http://bugzilla.kernel.org/show_bug.cgi?id=12793

Narendra Prasad Madanapalli <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |[email protected]

--- Comment #1 from Narendra Prasad Madanapalli <[email protected]> 2009-08-07 15:02:16 --- The following patch fixes the issue.

====Patch starts
iff -uNr linux-2.6.30.3-orig/fs/ext4/xattr.c linux-2.6.30.3-fix/fs/ext4/xattr.c

@@ -698,7 +698,7 @@
 #define header(x) ((struct ext4_xattr_header *)(x))
 
     if (i->value && i->value_len > sb->s_blocksize)
-        return -ENOSPC;
+        return -E2BIG;
     if (s->base) {
         ce = mb_cache_entry_get(ext4_xattr_cache, bs->bh->b_bdev,
                     bs->bh->b_blocknr);

====Patch ends

Ran test_xattr.py on the kernel with above fix, it terminates with OSError 7.

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http://bugzilla.kernel.org/show_bug.cgi?id=12793

Theodore Tso <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

                 CC|                            |[email protected]
         Regression|---                         |No

--- Comment #2 from Theodore Tso <[email protected]> 2009-08-11 02:58:18 --- I'm not convinced this change to use E2BIG instead of ENOSPC is always the
right thing. Consider the wording of E2BIG: "The value of the given attribute
is too large, IT EXCEEDS THE MAXIMUM ALLOWABLE SIZE OF AN ATTRIBUTE VALUE". In other words E2BIG implies that a request was made to create an attribute where the size exceeded some static value.

So if we pass in a request to create an attribute which is 2MB, E2BIG makes sense. On the other hand, if the EA block is almost full, a request to create an attribute value which is 2 bytes long could result in an error --- and in that case, ENOSPC makes a lot more sense that E2BIG.

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