[XFS] In actual allocation of file system blocks and freeing extents, the

transaction within each such operation may involve multiple locking of AGF
buffer. While the freeing extent function has sorted the extents based on
AGF number before entering into transaction, however, when the file system
space is very limited, the allocation of space would try every AGF to get
space allocated, this could potentially cause out-of-order locking, thus
deadlock could happen. This fix mitigates the scarce space for allocation
by setting aside a few blocks without reservation, and avoid deadlock by
maintaining ascending order of AGF locking.

SGI-PV: 947395
SGI-Modid: xfs-linux-melb:xfs-kern:210801a

Signed-off-by: Yingping Lu <yingping@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h
index 2d1f8928b267..650591f999ae 100644
--- a/fs/xfs/xfs_alloc.h
+++ b/fs/xfs/xfs_alloc.h
@@ -41,6 +41,7 @@ typedef enum xfs_alloctype
  * Flags for xfs_alloc_fix_freelist.
  */
 #define XFS_ALLOC_FLAG_TRYLOCK  0x00000001  /* use trylock for buffer locking */
+#define XFS_ALLOC_FLAG_FREEING  0x00000002  /* indicate caller is freeing extents*/
 
 /*
  * Argument structure for xfs_alloc routines.
@@ -70,6 +71,7 @@ typedef struct xfs_alloc_arg {
         char            wasfromfl;      /* set if allocation is from freelist */
         char            isfl;           /* set if is freelist blocks - !acctg */
         char            userdata;       /* set if this is user data */
+        xfs_fsblock_t   firstblock;     /* io first block allocated */
 } xfs_alloc_arg_t;
 
 /*