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[PATCH 1/3] xfs: only lock the rt bitmap inode once per allocation

To: xfs@xxxxxxxxxxx
Subject: [PATCH 1/3] xfs: only lock the rt bitmap inode once per allocation
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Tue, 25 Jan 2011 04:06:19 -0500
References: <20110125090618.432370964@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: quilt/0.48-1
Currently both xfs_rtpick_extent and xfs_rtallocate_extent call
xfs_trans_iget to grab and lock the rt bitmap inode, which results in a
deadlock since the removal of the lock recursion counters in commit

        "xfs: simplify inode to transaction joining"

Fix this by acquiring and locking the inode in xfs_bmap_rtalloc before
calling into xfs_rtpick_extent and xfs_rtallocate_extent.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Index: xfs/fs/xfs/xfs_bmap.c
===================================================================
--- xfs.orig/fs/xfs/xfs_bmap.c  2011-01-24 11:36:00.541016631 +0100
+++ xfs/fs/xfs/xfs_bmap.c       2011-01-24 16:02:40.581003990 +0100
@@ -2316,6 +2316,7 @@ xfs_bmap_rtalloc(
        xfs_extlen_t    prod = 0;       /* product factor for allocators */
        xfs_extlen_t    ralen = 0;      /* realtime allocation length */
        xfs_extlen_t    align;          /* minimum allocation alignment */
+       xfs_inode_t     *ip;            /* bitmap incore inode */
        xfs_rtblock_t   rtb;
 
        mp = ap->ip->i_mount;
@@ -2348,6 +2349,16 @@ xfs_bmap_rtalloc(
         */
        if (ralen * mp->m_sb.sb_rextsize >= MAXEXTLEN)
                ralen = MAXEXTLEN / mp->m_sb.sb_rextsize;
+
+       /*
+        * Lock out other modifications to the RT bitmap inode.
+        */
+       error = xfs_trans_iget(mp, ap->tp, mp->m_sb.sb_rbmino, 0,
+                              XFS_ILOCK_EXCL, &ip);
+       if (error)
+               return error;
+       ASSERT(ip == mp->m_rbmip);
+
        /*
         * If it's an allocation to an empty file at offset 0,
         * pick an extent that will space things out in the rt area.
Index: xfs/fs/xfs/xfs_rtalloc.c
===================================================================
--- xfs.orig/fs/xfs/xfs_rtalloc.c       2011-01-24 11:36:00.519026479 +0100
+++ xfs/fs/xfs/xfs_rtalloc.c    2011-01-24 16:02:30.086004688 +0100
@@ -2075,15 +2075,15 @@ xfs_rtallocate_extent(
        xfs_extlen_t    prod,           /* extent product factor */
        xfs_rtblock_t   *rtblock)       /* out: start block allocated */
 {
+       xfs_mount_t     *mp = tp->t_mountp;
        int             error;          /* error value */
-       xfs_inode_t     *ip;            /* inode for bitmap file */
-       xfs_mount_t     *mp;            /* file system mount structure */
        xfs_rtblock_t   r;              /* result allocated block */
        xfs_fsblock_t   sb;             /* summary file block number */
        xfs_buf_t       *sumbp;         /* summary file block buffer */
 
+       ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
        ASSERT(minlen > 0 && minlen <= maxlen);
-       mp = tp->t_mountp;
+
        /*
         * If prod is set then figure out what to do to minlen and maxlen.
         */
@@ -2099,12 +2099,7 @@ xfs_rtallocate_extent(
                        return 0;
                }
        }
-       /*
-        * Lock out other callers by grabbing the bitmap inode lock.
-        */
-       if ((error = xfs_trans_iget(mp, tp, mp->m_sb.sb_rbmino, 0,
-                                       XFS_ILOCK_EXCL, &ip)))
-               return error;
+
        sumbp = NULL;
        /*
         * Allocate by size, or near another block, or exactly at some block.
@@ -2123,11 +2118,12 @@ xfs_rtallocate_extent(
                                len, &sumbp, &sb, prod, &r);
                break;
        default:
+               error = EIO;
                ASSERT(0);
        }
-       if (error) {
+       if (error)
                return error;
-       }
+
        /*
         * If it worked, update the superblock.
         */
@@ -2306,20 +2302,16 @@ xfs_rtpick_extent(
        xfs_rtblock_t   *pick)          /* result rt extent */
 {
        xfs_rtblock_t   b;              /* result block */
-       int             error;          /* error return value */
-       xfs_inode_t     *ip;            /* bitmap incore inode */
        int             log2;           /* log of sequence number */
        __uint64_t      resid;          /* residual after log removed */
        __uint64_t      seq;            /* sequence number of file creation */
        __uint64_t      *seqp;          /* pointer to seqno in inode */
 
-       if ((error = xfs_trans_iget(mp, tp, mp->m_sb.sb_rbmino, 0,
-                                       XFS_ILOCK_EXCL, &ip)))
-               return error;
-       ASSERT(ip == mp->m_rbmip);
-       seqp = (__uint64_t *)&ip->i_d.di_atime;
-       if (!(ip->i_d.di_flags & XFS_DIFLAG_NEWRTBM)) {
-               ip->i_d.di_flags |= XFS_DIFLAG_NEWRTBM;
+       ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
+
+       seqp = (__uint64_t *)&mp->m_rbmip->i_d.di_atime;
+       if (!(mp->m_rbmip->i_d.di_flags & XFS_DIFLAG_NEWRTBM)) {
+               mp->m_rbmip->i_d.di_flags |= XFS_DIFLAG_NEWRTBM;
                *seqp = 0;
        }
        seq = *seqp;
@@ -2335,7 +2327,7 @@ xfs_rtpick_extent(
                        b = mp->m_sb.sb_rextents - len;
        }
        *seqp = seq + 1;
-       xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+       xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);
        *pick = b;
        return 0;
 }

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