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Patch "ext4: handle the rest of ext4_mb_load_buddy() ENOMEM errors" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Apr 10, 2018

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This is a note to let you know that I've just added the patch titled

ext4: handle the rest of ext4_mb_load_buddy() ENOMEM errors

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ext4-handle-the-rest-of-ext4_mb_load_buddy-enomem-errors.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Tue Apr 10 10:31:53 CEST 2018

From: Konstantin Khlebnikov <[email protected]>
Date: Sun, 21 May 2017 22:35:23 -0400
Subject: ext4: handle the rest of ext4_mb_load_buddy() ENOMEM errors

From: Konstantin Khlebnikov <[email protected]>

[ Upstream commit 9651e6b2e20648d04d5e1fe6479a3056047e8781 ]

I've got another report about breaking ext4 by ENOMEM error returned from ext4_mb_load_buddy() caused by memory shortage in memory cgroup. This time inside ext4_discard_preallocations().

This patch replaces ext4_error() with ext4_warning() where errors returned from ext4_mb_load_buddy() are not fatal and handled by caller:
* ext4_mb_discard_group_preallocations() - called before generating ENOSPC, we'll try to discard other group or return ENOSPC into user-space.
* ext4_trim_all_free() - just stop trimming and return ENOMEM from ioctl.

Some callers cannot handle errors, thus __GFP_NOFAIL is used for them:
* ext4_discard_preallocations()
* ext4_mb_discard_lg_preallocations()

Fixes adb7ef600cc9 ("ext4: use __GFP_NOFAIL in ext4_free_blocks()")
Signed-off-by Konstantin Khlebnikov <[email protected]>
Signed-off-by Theodore Ts'o <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 fs/ext4/mballoc.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)
fs/ext4/mballoc.c +14 -9
@@ -3874,7 +3874,8 @@ ext4_mb_discard_group_preallocations(str
 
 	err = ext4_mb_load_buddy(sb, group, &e4b);
 	if (err) {
-		ext4_error(sb, "Error loading buddy information for %u", group);
+		ext4_warning(sb, "Error %d loading buddy information for %u",
+			     err, group);
 		put_bh(bitmap_bh);
 		return 0;
 	}

@@ -4031,10 +4032,11 @@ repeat:
 		BUG_ON(pa->pa_type != MB_INODE_PA);
 		group = ext4_get_group_number(sb, pa->pa_pstart);
 
-		err = ext4_mb_load_buddy(sb, group, &e4b);
+		err = ext4_mb_load_buddy_gfp(sb, group, &e4b,
+					     GFP_NOFS|__GFP_NOFAIL);
 		if (err) {
-			ext4_error(sb, "Error loading buddy information for %u",
-					group);
+			ext4_error(sb, "Error %d loading buddy information for %u",
+				   err, group);
 			continue;
 		}
 

@@ -4290,11 +4292,14 @@ ext4_mb_discard_lg_preallocations(struct
 	spin_unlock(&lg->lg_prealloc_lock);
 
 	list_for_each_entry_safe(pa, tmp, &discard_list, u.pa_tmp_list) {
+		int err;
 
 		group = ext4_get_group_number(sb, pa->pa_pstart);
-		if (ext4_mb_load_buddy(sb, group, &e4b)) {
-			ext4_error(sb, "Error loading buddy information for %u",
-					group);
+		err = ext4_mb_load_buddy_gfp(sb, group, &e4b,
+					     GFP_NOFS|__GFP_NOFAIL);
+		if (err) {
+			ext4_error(sb, "Error %d loading buddy information for %u",
+				   err, group);
 			continue;
 		}
 		ext4_lock_group(sb, group);

@@ -5116,8 +5121,8 @@ ext4_trim_all_free(struct super_block *s
 
 	ret = ext4_mb_load_buddy(sb, group, &e4b);
 	if (ret) {
-		ext4_error(sb, "Error in loading buddy "
-				"information for %u", group);
+		ext4_warning(sb, "Error %d loading buddy information for %u",
+			     ret, group);
 		return ret;
 	}
 	bitmap = e4b.bd_bitmap;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/ext4-handle-the-rest-of-ext4_mb_load_buddy-enomem-errors.patch