[XFS] XFS: ASCII case-insensitive support

Implement ASCII case-insensitive support. It's primary purpose is for
supporting existing filesystems that already use this case-insensitive
mode migrated from IRIX. But, if you only need ASCII-only case-insensitive
support (ie. English only) and will never use another language, then this
mode is perfectly adequate.

ASCII-CI is implemented by generating hashes based on lower-case letters
and doing lower-case compares. It implements a new xfs_nameops vector for
doing the hashes and comparisons for all filename operations.

To create a filesystem with this CI mode, use: # mkfs.xfs -n version=ci
<device>

SGI-PV: 981516
SGI-Modid: xfs-linux-melb:xfs-kern:31209a

Signed-off-by: Barry Naujok <bnaujok@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>

6 files changed, 68 insertions, 4 deletions

diff --git a/fs/xfs/linux-2.6/xfs_linux.h b/fs/xfs/linux-2.6/xfs_linux.h
index 4edc46915b57..aded57321b12 100644
--- a/fs/xfs/linux-2.6/xfs_linux.h
+++ b/fs/xfs/linux-2.6/xfs_linux.h
@@ -76,6 +76,7 @@
 #include <linux/log2.h>
 #include <linux/spinlock.h>
 #include <linux/random.h>
+#include <linux/ctype.h>
 
 #include <asm/page.h>
 #include <asm/div64.h>
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 41eea24a46e4..cce59cc6e748 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -569,7 +569,10 @@ xfs_set_inodeops(
                 inode->i_mapping->a_ops = &xfs_address_space_operations;
                 break;
         case S_IFDIR:
-                inode->i_op = &xfs_dir_inode_operations;
+                if (xfs_sb_version_hasasciici(&XFS_M(inode->i_sb)->m_sb))
+                        inode->i_op = &xfs_dir_ci_inode_operations;
+                else
+                        inode->i_op = &xfs_dir_inode_operations;
                 inode->i_fop = &xfs_dir_file_operations;
                 break;
         case S_IFLNK:
diff --git a/fs/xfs/xfs_dir2.c b/fs/xfs/xfs_dir2.c
index 882609c699c8..b445ec314764 100644
--- a/fs/xfs/xfs_dir2.c
+++ b/fs/xfs/xfs_dir2.c
@@ -48,6 +48,52 @@ struct xfs_name xfs_name_dotdot = {"..", 2};
 
 extern const struct xfs_nameops xfs_default_nameops;
 
+/*
+ * ASCII case-insensitive (ie. A-Z) support for directories that was
+ * used in IRIX.
+ */
+STATIC xfs_dahash_t
+xfs_ascii_ci_hashname(
+        struct xfs_name *name)
+{
+        xfs_dahash_t    hash;
+        int             i;
+
+        for (i = 0, hash = 0; i < name->len; i++)
+                hash = tolower(name->name[i]) ^ rol32(hash, 7);
+
+        return hash;
+}
+
+STATIC enum xfs_dacmp
+xfs_ascii_ci_compname(
+        struct xfs_da_args *args,
+        const char      *name,
+        int             len)
+{
+        enum xfs_dacmp  result;
+        int             i;
+
+        if (args->namelen != len)
+                return XFS_CMP_DIFFERENT;
+
+        result = XFS_CMP_EXACT;
+        for (i = 0; i < len; i++) {
+                if (args->name[i] == name[i])
+                        continue;
+                if (tolower(args->name[i]) != tolower(name[i]))
+                        return XFS_CMP_DIFFERENT;
+                result = XFS_CMP_CASE;
+        }
+
+        return result;
+}
+
+static struct xfs_nameops xfs_ascii_ci_nameops = {
+        .hashname       = xfs_ascii_ci_hashname,
+        .compname       = xfs_ascii_ci_compname,
+};
+
 void
 xfs_dir_mount(
         xfs_mount_t     *mp)
@@ -67,7 +113,10 @@ xfs_dir_mount(
                 (mp->m_dirblksize - (uint)sizeof(xfs_da_node_hdr_t)) /
                 (uint)sizeof(xfs_da_node_entry_t);
         mp->m_dir_magicpct = (mp->m_dirblksize * 37) / 100;
-        mp->m_dirnameops = &xfs_default_nameops;
+        if (xfs_sb_version_hasasciici(&mp->m_sb))
+                mp->m_dirnameops = &xfs_ascii_ci_nameops;
+        else
+                mp->m_dirnameops = &xfs_default_nameops;
 }
 
 /*
diff --git a/fs/xfs/xfs_fs.h b/fs/xfs/xfs_fs.h
index 3bed6433d050..6ca749897c58 100644
--- a/fs/xfs/xfs_fs.h
+++ b/fs/xfs/xfs_fs.h
@@ -239,6 +239,7 @@ typedef struct xfs_fsop_resblks {
 #define XFS_FSOP_GEOM_FLAGS_LOGV2       0x0100  /* log format version 2 */
 #define XFS_FSOP_GEOM_FLAGS_SECTOR      0x0200  /* sector sizes >1BB    */
 #define XFS_FSOP_GEOM_FLAGS_ATTR2       0x0400  /* inline attributes rework */
+#define XFS_FSOP_GEOM_FLAGS_DIRV2CI     0x1000  /* ASCII only CI names */
 #define XFS_FSOP_GEOM_FLAGS_LAZYSB      0x4000  /* lazy superblock counters */
 
 
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 381ebda4f7bc..84583cf73db3 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -95,6 +95,8 @@ xfs_fs_geometry(
                                 XFS_FSOP_GEOM_FLAGS_DIRV2 : 0) |
                         (xfs_sb_version_hassector(&mp->m_sb) ?
                                 XFS_FSOP_GEOM_FLAGS_SECTOR : 0) |
+                        (xfs_sb_version_hasasciici(&mp->m_sb) ?
+                                XFS_FSOP_GEOM_FLAGS_DIRV2CI : 0) |
                         (xfs_sb_version_haslazysbcount(&mp->m_sb) ?
                                 XFS_FSOP_GEOM_FLAGS_LAZYSB : 0) |
                         (xfs_sb_version_hasattr2(&mp->m_sb) ?
@@ -625,7 +627,7 @@ xfs_fs_goingdown(
                         xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);
                         thaw_bdev(sb->s_bdev, sb);
                 }
-        
+
                 break;
         }
         case XFS_FSOP_GOING_FLAGS_LOGFLUSH:
diff --git a/fs/xfs/xfs_sb.h b/fs/xfs/xfs_sb.h
index e3204a36a222..3f8cf1587f4c 100644
--- a/fs/xfs/xfs_sb.h
+++ b/fs/xfs/xfs_sb.h
@@ -46,10 +46,12 @@ struct xfs_mount;
 #define XFS_SB_VERSION_SECTORBIT        0x0800
 #define XFS_SB_VERSION_EXTFLGBIT        0x1000
 #define XFS_SB_VERSION_DIRV2BIT         0x2000
+#define XFS_SB_VERSION_BORGBIT          0x4000  /* ASCII only case-insens. */
 #define XFS_SB_VERSION_MOREBITSBIT      0x8000
 #define XFS_SB_VERSION_OKSASHFBITS      \
         (XFS_SB_VERSION_EXTFLGBIT | \
-         XFS_SB_VERSION_DIRV2BIT)
+         XFS_SB_VERSION_DIRV2BIT | \
+         XFS_SB_VERSION_BORGBIT)
 #define XFS_SB_VERSION_OKREALFBITS      \
         (XFS_SB_VERSION_ATTRBIT | \
          XFS_SB_VERSION_NLINKBIT | \
@@ -437,6 +439,12 @@ static inline int xfs_sb_version_hassector(xfs_sb_t *sbp)
                 ((sbp)->sb_versionnum & XFS_SB_VERSION_SECTORBIT);
 }
 
+static inline int xfs_sb_version_hasasciici(xfs_sb_t *sbp)
+{
+        return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_4) && \
+                (sbp->sb_versionnum & XFS_SB_VERSION_BORGBIT);
+}
+
 static inline int xfs_sb_version_hasmorebits(xfs_sb_t *sbp)
 {
         return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_4) && \