+ jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     Subject: jbd2: mark the transaction context with the scope GFP_NOFS context
has been added to the -mm tree.  Its filename is
     jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context.patch

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------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: jbd2: mark the transaction context with the scope GFP_NOFS context

now that we have memalloc_nofs_{save,restore} api we can mark the whole
transaction context as implicitly GFP_NOFS.  All allocations will
automatically inherit GFP_NOFS this way.  This means that we do not have
to mark any of those requests with GFP_NOFS and moreover all the
ext4_kv[mz]alloc(GFP_NOFS) are also safe now because even the hardcoded
GFP_KERNEL allocations deep inside the vmalloc will be NOFS now.

Link: http://lkml.kernel.org/r/20170306131408.9828-7-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Chris Mason <clm@xxxxxx>
Cc: David Sterba <dsterba@xxxxxxx>
Cc: Brian Foster <bfoster@xxxxxxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Nikolay Borisov <nborisov@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/jbd2/transaction.c |   12 ++++++++++++
 include/linux/jbd2.h  |    2 ++
 2 files changed, 14 insertions(+)

diff -puN fs/jbd2/transaction.c~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context fs/jbd2/transaction.c
--- a/fs/jbd2/transaction.c~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context
+++ a/fs/jbd2/transaction.c
@@ -29,6 +29,7 @@
 #include <linux/backing-dev.h>
 #include <linux/bug.h>
 #include <linux/module.h>
+#include <linux/sched/mm.h>
 
 #include <trace/events/jbd2.h>
 
@@ -388,6 +389,11 @@ repeat:
 
 	rwsem_acquire_read(&journal->j_trans_commit_map, 0, 0, _THIS_IP_);
 	jbd2_journal_free_transaction(new_transaction);
+	/*
+	 * Make sure that no allocations done while the transaction is
+	 * open is going to recurse back to the fs layer.
+	 */
+	handle->saved_alloc_context = memalloc_nofs_save();
 	return 0;
 }
 
@@ -466,6 +472,7 @@ handle_t *jbd2__journal_start(journal_t
 	trace_jbd2_handle_start(journal->j_fs_dev->bd_dev,
 				handle->h_transaction->t_tid, type,
 				line_no, nblocks);
+
 	return handle;
 }
 EXPORT_SYMBOL(jbd2__journal_start);
@@ -1760,6 +1767,11 @@ int jbd2_journal_stop(handle_t *handle)
 	if (handle->h_rsv_handle)
 		jbd2_journal_free_reserved(handle->h_rsv_handle);
 free_and_exit:
+	/*
+	 * scope of th GFP_NOFS context is over here and so we can
+	 * restore the original alloc context.
+	 */
+	memalloc_nofs_restore(handle->saved_alloc_context);
 	jbd2_free_handle(handle);
 	return err;
 }
diff -puN include/linux/jbd2.h~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context include/linux/jbd2.h
--- a/include/linux/jbd2.h~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context
+++ a/include/linux/jbd2.h
@@ -491,6 +491,8 @@ struct jbd2_journal_handle
 
 	unsigned long		h_start_jiffies;
 	unsigned int		h_requested_credits;
+
+	unsigned int		saved_alloc_context;
 };
 
 
_

Patches currently in -mm which might be from mhocko@xxxxxxxx are

lockdep-allow-to-disable-reclaim-lockup-detection.patch
xfs-abstract-pf_fstrans-to-pf_memalloc_nofs.patch
mm-introduce-memalloc_nofs_saverestore-api.patch
xfs-use-memalloc_nofs_saverestore-instead-of-memalloc_noio.patch
jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context.patch
jbd2-make-the-whole-kjournald2-kthread-nofs-safe.patch

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