libxfs: handle read errors in libxfs_trans_read_buf

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@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

diff --git a/libxfs/trans.c b/libxfs/trans.c
index 2b1c80684f6311b83e00fcf7a428c3be37b75b40..86a6ac7fdace127a9afd5dc656d7c9aee895f9e1 100644 (file)
--- a/libxfs/trans.c
+++ b/libxfs/trans.c
@@ -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;
 }