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* This automated bisection report was sent to you on the basis  *
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mainline/master bisection: baseline.login on odroid-xu3

Summary:
  Start:      b3a608222336 Merge branch 'for-v5.6' of git://git.kernel.org:/pub/scm/linux/kernel/git/jmorris/linux-security
  Plain log:  https://storage.kernelci.org//mainline/master/v5.5-3996-gb3a608222336/arm/multi_v7_defconfig+CONFIG_SMP=n/gcc-8/lab-collabora/baseline-exynos5422-odroidxu3.txt
  HTML log:   https://storage.kernelci.org//mainline/master/v5.5-3996-gb3a608222336/arm/multi_v7_defconfig+CONFIG_SMP=n/gcc-8/lab-collabora/baseline-exynos5422-odroidxu3.html
  Result:     71723a96b8b1 dmaengine: Create symlinks between DMA channels and slaves

Checks:
  revert:     PASS
  verify:     PASS

Parameters:
  Tree:       mainline
  URL:        git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
  Branch:     master
  Target:     odroid-xu3
  CPU arch:   arm
  Lab:        lab-collabora
  Compiler:   gcc-8
  Config:     multi_v7_defconfig+CONFIG_SMP=n
  Test case:  baseline.login

Breaking commit found:

-------------------------------------------------------------------------------
commit 71723a96b8b1367fefc18f60025dae792477d602
Author: Geert Uytterhoeven [off-list ref]
Date:   Fri Jan 17 16:30:56 2020 +0100

    dmaengine: Create symlinks between DMA channels and slaves
    
    Currently it is not easy to find out which DMA channels are in use, and
    which slave devices are using which channels.
    
    Fix this by creating two symlinks between the DMA channel and the actual
    slave device when a channel is requested:
      1. A "slave" symlink from DMA channel to slave device,
      2. A "dma:<name>" symlink slave device to DMA channel.
    When the channel is released, the symlinks are removed again.
    The latter requires keeping track of the slave device and the channel
    name in the dma_chan structure.
    
    Note that this is limited to channel request functions for requesting an
    exclusive slave channel that take a device pointer (dma_request_chan()
    and dma_request_slave_channel*()).
    
    Signed-off-by: Geert Uytterhoeven [off-list ref]
    Tested-by: Niklas Söderlund [off-list ref]
    Link: https://lore.kernel.org/r/20200117153056.31363-1-geert+renesas@glider.be (local)
    Signed-off-by: Vinod Koul [off-list ref]

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 51a2f2b1b2de..f3ef4edd4de1 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c

@@ -60,6 +60,8 @@ static long dmaengine_ref_count;
 
 /* --- sysfs implementation --- */
 
+#define DMA_SLAVE_NAME	"slave"
+
 /**
  * dev_to_dma_chan - convert a device pointer to its sysfs container object
  * @dev - device node

@@ -730,11 +732,11 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
 	if (has_acpi_companion(dev) && !chan)
 		chan = acpi_dma_request_slave_chan_by_name(dev, name);
 
-	if (chan) {
-		/* Valid channel found or requester needs to be deferred */
-		if (!IS_ERR(chan) || PTR_ERR(chan) == -EPROBE_DEFER)
-			return chan;
-	}
+	if (PTR_ERR(chan) == -EPROBE_DEFER)
+		return chan;
+
+	if (!IS_ERR_OR_NULL(chan))
+		goto found;
 
 	/* Try to find the channel via the DMA filter map(s) */
 	mutex_lock(&dma_list_mutex);

@@ -754,7 +756,23 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
 	}
 	mutex_unlock(&dma_list_mutex);
 
-	return chan ? chan : ERR_PTR(-EPROBE_DEFER);
+	if (!IS_ERR_OR_NULL(chan))
+		goto found;
+
+	return ERR_PTR(-EPROBE_DEFER);
+
+found:
+	chan->slave = dev;
+	chan->name = kasprintf(GFP_KERNEL, "dma:%s", name);
+	if (!chan->name)
+		return ERR_PTR(-ENOMEM);
+
+	if (sysfs_create_link(&chan->dev->device.kobj, &dev->kobj,
+			      DMA_SLAVE_NAME))
+		dev_err(dev, "Cannot create DMA %s symlink\n", DMA_SLAVE_NAME);
+	if (sysfs_create_link(&dev->kobj, &chan->dev->device.kobj, chan->name))
+		dev_err(dev, "Cannot create DMA %s symlink\n", chan->name);
+	return chan;
 }
 EXPORT_SYMBOL_GPL(dma_request_chan);
 

@@ -812,6 +830,13 @@ void dma_release_channel(struct dma_chan *chan)
 	/* drop PRIVATE cap enabled by __dma_request_channel() */
 	if (--chan->device->privatecnt == 0)
 		dma_cap_clear(DMA_PRIVATE, chan->device->cap_mask);
+	if (chan->slave) {
+		sysfs_remove_link(&chan->slave->kobj, chan->name);
+		kfree(chan->name);
+		chan->name = NULL;
+		chan->slave = NULL;
+	}
+	sysfs_remove_link(&chan->dev->device.kobj, DMA_SLAVE_NAME);
 	mutex_unlock(&dma_list_mutex);
 }
 EXPORT_SYMBOL_GPL(dma_release_channel);

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index f52f274773ed..fef69a9c5824 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h

@@ -294,10 +294,12 @@ struct dma_router {
 /**
  * struct dma_chan - devices supply DMA channels, clients use them
  * @device: ptr to the dma device who supplies this channel, always !%NULL
+ * @slave: ptr to the device using this channel
  * @cookie: last cookie value returned to client
  * @completed_cookie: last completed cookie for this channel
  * @chan_id: channel ID for sysfs
  * @dev: class device for sysfs
+ * @name: backlink name for sysfs
  * @device_node: used to add this to the device chan list
  * @local: per-cpu pointer to a struct dma_chan_percpu
  * @client_count: how many clients are using this channel

@@ -308,12 +310,14 @@ struct dma_router {
  */
 struct dma_chan {
 	struct dma_device *device;
+	struct device *slave;
 	dma_cookie_t cookie;
 	dma_cookie_t completed_cookie;
 
 	/* sysfs */
 	int chan_id;
 	struct dma_chan_dev *dev;
+	const char *name;
 
 	struct list_head device_node;
 	struct dma_chan_percpu __percpu *local;
-------------------------------------------------------------------------------

Git bisection log:

-------------------------------------------------------------------------------
git bisect start
# good: [4703d9119972bf586d2cca76ec6438f819ffa30e] Merge tag 'xarray-5.5' of git://git.infradead.org/users/willy/linux-dax
git bisect good 4703d9119972bf586d2cca76ec6438f819ffa30e
# bad: [b3a6082223369203d7e7db7e81253ac761377644] Merge branch 'for-v5.6' of git://git.kernel.org:/pub/scm/linux/kernel/git/jmorris/linux-security
git bisect bad b3a6082223369203d7e7db7e81253ac761377644
# bad: [a78208e2436963d0b2c7d186277d6e1a9755029a] Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
git bisect bad a78208e2436963d0b2c7d186277d6e1a9755029a
# bad: [b1dba2473114588be3df916bf629a61bdcc83737] Merge tag 'selinux-pr-20200127' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
git bisect bad b1dba2473114588be3df916bf629a61bdcc83737
# good: [9e1af7567b266dc6c3c8fd434ea807b3206bfdc1] Merge tag 'mmc-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc
git bisect good 9e1af7567b266dc6c3c8fd434ea807b3206bfdc1
# bad: [aae1464f46a2403565f75717438118691d31ccf1] Merge tag 'regulator-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator
git bisect bad aae1464f46a2403565f75717438118691d31ccf1
# bad: [a5b871c91d470326eed3ae0ebd2fc07f3aee9050] Merge tag 'dmaengine-5.6-rc1' of git://git.infradead.org/users/vkoul/slave-dma
git bisect bad a5b871c91d470326eed3ae0ebd2fc07f3aee9050
# good: [12fb2b993e1508a0d9032a2314dfdda2a3a5535e] Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid
git bisect good 12fb2b993e1508a0d9032a2314dfdda2a3a5535e
# good: [7d083ae983573de16e3ab0bfd47486996d211417] dmaengine: doc: Add sections for per descriptor metadata support
git bisect good 7d083ae983573de16e3ab0bfd47486996d211417
# good: [e606c8b9d751e593b71bdcb636ac3392c62c1c50] dmaengine: s3c24xx-dma: fix spelling mistake "to" -> "too"
git bisect good e606c8b9d751e593b71bdcb636ac3392c62c1c50
# good: [8f47d1a5e545f903cd049c42da31a3be36178447] dmaengine: idxd: connect idxd to dmaengine subsystem
git bisect good 8f47d1a5e545f903cd049c42da31a3be36178447
# good: [f46e49a9cc3814f3564477f0fffc00e0a2bc9e80] livepatch: Handle allocation failure in the sample of shadow variable API
git bisect good f46e49a9cc3814f3564477f0fffc00e0a2bc9e80
# good: [e9f08b65250d73ab70e79e194813f52b8d306784] dmaengine: hisilicon: Add Kunpeng DMA engine support
git bisect good e9f08b65250d73ab70e79e194813f52b8d306784
# bad: [71723a96b8b1367fefc18f60025dae792477d602] dmaengine: Create symlinks between DMA channels and slaves
git bisect bad 71723a96b8b1367fefc18f60025dae792477d602
# first bad commit: [71723a96b8b1367fefc18f60025dae792477d602] dmaengine: Create symlinks between DMA channels and slaves
-------------------------------------------------------------------------------