[PATCH 1/4] libxfs: handle read errors in libxfs_trans_read_buf

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

Libxfs_readbuf may return a NULL buffer to indicate that an error happend
during the read, but we currently ignore that if libxfs_trans_read_buf
is called with a NULL transaction pointer.  Fix this by copying the
relevant code from the kernel version of the routine, and also tidy
the code up a bit by using a common exit label.

This fixes a regression that was introduced in xfsprogs 3.0.0 by commit

        "Implement buffer and inode caching in libxfs, groundwork for a
         parallel version of xfs_repair."

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

Index: xfsprogs-dev/libxfs/trans.c
===================================================================
--- xfsprogs-dev.orig/libxfs/trans.c    2011-09-20 20:33:48.000000000 +0000
+++ xfsprogs-dev/libxfs/trans.c 2011-09-20 20:35:24.000000000 +0000
@@ -478,9 +478,15 @@ libxfs_trans_read_buf(
        xfs_buf_log_item_t      *bip;
        xfs_buftarg_t           bdev;
 
+       *bpp = NULL;
+
        if (tp == NULL) {
-               *bpp = libxfs_readbuf(dev, blkno, len, flags);
-               return 0;
+               bp = libxfs_readbuf(dev, blkno, len, flags);
+               if (!bp) {
+                       return (flags & XBF_TRYLOCK) ?
+                               EAGAIN : XFS_ERROR(ENOMEM);
+               }
+               goto done;
        }
 
        bdev.dev = dev;
@@ -490,15 +496,15 @@ libxfs_trans_read_buf(
                ASSERT(XFS_BUF_FSPRIVATE(bp, void *) != NULL);
                bip = XFS_BUF_FSPRIVATE(bp, xfs_buf_log_item_t*);
                bip->bli_recur++;
-               *bpp = bp;
-               return 0;
+               goto done;
        }
 
        bp = libxfs_readbuf(dev, blkno, len, flags);
-       if (!bp){
-               *bpp = NULL;
-               return errno;
-       }
+       if (!bp) {
+               return (flags & XBF_TRYLOCK) ?
+                       EAGAIN : XFS_ERROR(ENOMEM);
+       }
+
 #ifdef XACT_DEBUG
        fprintf(stderr, "trans_read_buf buffer %p, transaction %p\n", bp, tp);
 #endif
@@ -510,6 +516,7 @@ libxfs_trans_read_buf(
 
        /* initialise b_fsprivate2 so we can find it incore */
        XFS_BUF_SET_FSPRIVATE2(bp, tp);
+done:
        *bpp = bp;
        return 0;
 }