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Re: [PATCH 4/4] xfs: increase number of ACL entries for V5 superblocks

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 4/4] xfs: increase number of ACL entries for V5 superblocks
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Wed, 05 Jun 2013 08:26:01 -0500
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1370398150-12084-5-git-send-email-david@xxxxxxxxxxxxx>
References: <1370398150-12084-1-git-send-email-david@xxxxxxxxxxxxx> <1370398150-12084-5-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0
On 06/04/13 21:09, Dave Chinner wrote:
From: Dave Chinner<dchinner@xxxxxxxxxx>

The limit of 25 ACL entries is arbitrary, but baked into the on-disk
format.  For version 5 superblocks, increase it to the maximum nuber
of ACLs that can fit into a single xattr.

Signed-off-by: Dave Chinner<dchinner@xxxxxxxxxx>
Reviewed-by: Brian Foster<bfoster@xxxxxxxxxx>
---

  /* On-disk XFS access control list structure */
+struct xfs_acl_entry {
+       __be32  ae_tag;
+       __be32  ae_id;
+       __be16  ae_perm;
+       __be16  ae_pad;         /* fill the implicit hole in the structure */
+};
+
  struct xfs_acl {
-       __be32          acl_cnt;
-       struct xfs_acl_entry {
-               __be32  ae_tag;
-               __be32  ae_id;
-               __be16  ae_perm;
-       } acl_entry[XFS_ACL_MAX_ENTRIES];
+       __be32                  acl_cnt;
+       struct xfs_acl_entry    acl_entry[0];
  };

+/*
+ * The number of ACL entries allowed is defined by the on-disk format.
+ * For v4 superblocks, that is limited to 25 entries. For v5 superblocks, it is
+ * limited only by the maximum size of the xattr that stores the information.
+ */
+#define XFS_ACL_MAX_ENTRIES(mp)        \
+       (xfs_sb_version_hascrc(&mp->m_sb) \
+               ?  (XATTR_SIZE_MAX - sizeof(struct xfs_acl)) / \
+                                               sizeof(struct xfs_acl_entry) \
+               : 25)
+
+#define XFS_ACL_MAX_SIZE(mp) \
+       (sizeof(struct xfs_acl) + \
+               sizeof(struct xfs_acl_entry) * XFS_ACL_MAX_ENTRIES((mp)))
+
  /* On-disk XFS extended attribute names */
  #define SGI_ACL_FILE          (unsigned char *)"SGI_ACL_FILE"
  #define SGI_ACL_DEFAULT               (unsigned char *)"SGI_ACL_DEFAULT"

I thought you would leave the XFS_ACL_MAX_ENTRIES(mp) as:


#define XFS_ACL_MAX_ENTRIES(mp) \
        (xfs_sb_version_hascrc(&mp->m_sb) \
           ?  (XATTR_SIZE_MAX - sizeof(__be32)) / sizeof(struct xfs_acl_entry) \
           : 25)

and change the XFS_ACL_SIZE to:

#define XFS_ACL_SIZE(mp) \
        ((offsetof(struct xfs_acl_entry, acl_entry) + \
                sizeof(struct xfs_acl_entry) *

since acl_entry[] is a place holder for the entry array.

--Mark.

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