[XFS] shrink mrlock_t

The writer field is not needed for non_DEBU builds so remove it. While
we're at i also clean up the interface for is locked asserts to go through
and xfs_iget.c helper with an interface like the xfs_ilock routines to
isolated the XFS codebase from mrlock internals. That way we can kill
mrlock_t entirely once rw_semaphores grow an islocked facility. Also
remove unused flags to the ilock family of functions.

SGI-PV: 976035
SGI-Modid: xfs-linux-melb:xfs-kern:30902a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

2 files changed, 33 insertions, 48 deletions

diff --git a/fs/xfs/linux-2.6/mrlock.h b/fs/xfs/linux-2.6/mrlock.h
index c110bb002665..ff6a19873e5c 100644
--- a/fs/xfs/linux-2.6/mrlock.h
+++ b/fs/xfs/linux-2.6/mrlock.h
@@ -20,29 +20,24 @@
 
 #include <linux/rwsem.h>
 
-enum { MR_NONE, MR_ACCESS, MR_UPDATE };
-
 typedef struct {
         struct rw_semaphore     mr_lock;
+#ifdef DEBUG
         int                     mr_writer;
+#endif
 } mrlock_t;
 
+#ifdef DEBUG
 #define mrinit(mrp, name)       \
         do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)
+#else
+#define mrinit(mrp, name)       \
+        do { init_rwsem(&(mrp)->mr_lock); } while (0)
+#endif
+
 #define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
 #define mrfree(mrp)             do { } while (0)
 
-static inline void mraccess(mrlock_t *mrp)
-{
-        down_read(&mrp->mr_lock);
-}
-
-static inline void mrupdate(mrlock_t *mrp)
-{
-        down_write(&mrp->mr_lock);
-        mrp->mr_writer = 1;
-}
-
 static inline void mraccess_nested(mrlock_t *mrp, int subclass)
 {
         down_read_nested(&mrp->mr_lock, subclass);
@@ -51,10 +46,11 @@ static inline void mraccess_nested(mrlock_t *mrp, int subclass)
 static inline void mrupdate_nested(mrlock_t *mrp, int subclass)
 {
         down_write_nested(&mrp->mr_lock, subclass);
+#ifdef DEBUG
         mrp->mr_writer = 1;
+#endif
 }
 
-
 static inline int mrtryaccess(mrlock_t *mrp)
 {
         return down_read_trylock(&mrp->mr_lock);
@@ -64,39 +60,31 @@ static inline int mrtryupdate(mrlock_t *mrp)
 {
         if (!down_write_trylock(&mrp->mr_lock))
                 return 0;
+#ifdef DEBUG
         mrp->mr_writer = 1;
+#endif
         return 1;
 }
 
-static inline void mrunlock(mrlock_t *mrp)
+static inline void mrunlock_excl(mrlock_t *mrp)
 {
-        if (mrp->mr_writer) {
-                mrp->mr_writer = 0;
-                up_write(&mrp->mr_lock);
-        } else {
-                up_read(&mrp->mr_lock);
-        }
+#ifdef DEBUG
+        mrp->mr_writer = 0;
+#endif
+        up_write(&mrp->mr_lock);
 }
 
-static inline void mrdemote(mrlock_t *mrp)
+static inline void mrunlock_shared(mrlock_t *mrp)
 {
-        mrp->mr_writer = 0;
-        downgrade_write(&mrp->mr_lock);
+        up_read(&mrp->mr_lock);
 }
 
-#ifdef DEBUG
-/*
- * Debug-only routine, without some platform-specific asm code, we can
- * now only answer requests regarding whether we hold the lock for write
- * (reader state is outside our visibility, we only track writer state).
- * Note: means !ismrlocked would give false positives, so don't do that.
- */
-static inline int ismrlocked(mrlock_t *mrp, int type)
+static inline void mrdemote(mrlock_t *mrp)
 {
-        if (mrp && type == MR_UPDATE)
-                return mrp->mr_writer;
-        return 1;
-}
+#ifdef DEBUG
+        mrp->mr_writer = 0;
 #endif
+        downgrade_write(&mrp->mr_lock);
+}
 
 #endif /* __XFS_SUPPORT_MRLOCK_H__ */
diff --git a/fs/xfs/linux-2.6/xfs_lrw.c b/fs/xfs/linux-2.6/xfs_lrw.c
index 1ebd8004469c..5e3b57516ec7 100644
--- a/fs/xfs/linux-2.6/xfs_lrw.c
+++ b/fs/xfs/linux-2.6/xfs_lrw.c
@@ -394,7 +394,7 @@ xfs_zero_last_block(
         int             error = 0;
         xfs_bmbt_irec_t imap;
 
-        ASSERT(ismrlocked(&ip->i_lock, MR_UPDATE) != 0);
+        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
 
         zero_offset = XFS_B_FSB_OFFSET(mp, isize);
         if (zero_offset == 0) {
@@ -425,14 +425,14 @@ xfs_zero_last_block(
          * out sync.  We need to drop the ilock while we do this so we
          * don't deadlock when the buffer cache calls back to us.
          */
-        xfs_iunlock(ip, XFS_ILOCK_EXCL| XFS_EXTSIZE_RD);
+        xfs_iunlock(ip, XFS_ILOCK_EXCL);
 
         zero_len = mp->m_sb.sb_blocksize - zero_offset;
         if (isize + zero_len > offset)
                 zero_len = offset - isize;
         error = xfs_iozero(ip, isize, zero_len);
 
-        xfs_ilock(ip, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);
+        xfs_ilock(ip, XFS_ILOCK_EXCL);
         ASSERT(error >= 0);
         return error;
 }
@@ -465,8 +465,7 @@ xfs_zero_eof(
         int             error = 0;
         xfs_bmbt_irec_t imap;
 
-        ASSERT(ismrlocked(&ip->i_lock, MR_UPDATE));
-        ASSERT(ismrlocked(&ip->i_iolock, MR_UPDATE));
+        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_IOLOCK_EXCL));
         ASSERT(offset > isize);
 
         /*
@@ -475,8 +474,7 @@ xfs_zero_eof(
          */
         error = xfs_zero_last_block(ip, offset, isize);
         if (error) {
-                ASSERT(ismrlocked(&ip->i_lock, MR_UPDATE));
-                ASSERT(ismrlocked(&ip->i_iolock, MR_UPDATE));
+                ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_IOLOCK_EXCL));
                 return error;
         }
 
@@ -507,8 +505,7 @@ xfs_zero_eof(
                 error = xfs_bmapi(NULL, ip, start_zero_fsb, zero_count_fsb,
                                   0, NULL, 0, &imap, &nimaps, NULL, NULL);
                 if (error) {
-                        ASSERT(ismrlocked(&ip->i_lock, MR_UPDATE));
-                        ASSERT(ismrlocked(&ip->i_iolock, MR_UPDATE));
+                        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_IOLOCK_EXCL));
                         return error;
                 }
                 ASSERT(nimaps > 0);
@@ -532,7 +529,7 @@ xfs_zero_eof(
                  * Drop the inode lock while we're doing the I/O.
                  * We'll still have the iolock to protect us.
                  */
-                xfs_iunlock(ip, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);
+                xfs_iunlock(ip, XFS_ILOCK_EXCL);
 
                 zero_off = XFS_FSB_TO_B(mp, start_zero_fsb);
                 zero_len = XFS_FSB_TO_B(mp, imap.br_blockcount);
@@ -548,13 +545,13 @@ xfs_zero_eof(
                 start_zero_fsb = imap.br_startoff + imap.br_blockcount;
                 ASSERT(start_zero_fsb <= (end_zero_fsb + 1));
 
-                xfs_ilock(ip, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);
+                xfs_ilock(ip, XFS_ILOCK_EXCL);
         }
 
         return 0;
 
 out_lock:
-        xfs_ilock(ip, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);
+        xfs_ilock(ip, XFS_ILOCK_EXCL);
         ASSERT(error >= 0);
         return error;
 }