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Subject[PATCH] USB: gadget: f_mass_storage: Fix empty device release callback
This commit replaces an empty device releases callback with
one that uses reference counter to free underlying memory
only when the device is no longer used.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
---
drivers/usb/gadget/f_mass_storage.c | 87 +++++++++++++++++++++++------------
1 files changed, 57 insertions(+), 30 deletions(-)
This is put on top of the other 7 patches I sent earlier.

Noticed this after the put_device() fix, turns out 9-hour flight is
just perfect for fixing bugs (that, plus movies were boring).

Greg,

It seems it does not qualify for stable (too long); if you decide to pull
it into stable anyway (since a lot changes are just a simple
s/luns/luns->arr/) drop me a line so I'll rebase it.

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index b5dbb23..a3f7e71 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -349,9 +349,6 @@ struct fsg_common {
struct fsg_dev *fsg, *new_fsg;
wait_queue_head_t fsg_wait;

- /* filesem protects: backing files in use */
- struct rw_semaphore filesem;
-
/* lock protects: state, all the req_busy's */
spinlock_t lock;

@@ -368,7 +365,12 @@ struct fsg_common {

unsigned int nluns;
unsigned int lun;
- struct fsg_lun *luns;
+ struct fsg_luns {
+ /* filesem protects: backing files in use */
+ struct rw_semaphore filesem;
+ struct kref ref;
+ struct fsg_lun arr[];
+ } *luns;
struct fsg_lun *curlun;

unsigned int bulk_out_maxpacket;
@@ -1465,22 +1467,22 @@ static int do_start_stop(struct fsg_common *common)
/* Simulate an unload/eject */
if (common->ops && common->ops->pre_eject) {
int r = common->ops->pre_eject(common, curlun,
- curlun - common->luns);
+ curlun - common->luns->arr);
if (unlikely(r < 0))
return r;
else if (r)
return 0;
}

- up_read(&common->filesem);
- down_write(&common->filesem);
+ up_read(&common->luns->filesem);
+ down_write(&common->luns->filesem);
fsg_lun_close(curlun);
- up_write(&common->filesem);
- down_read(&common->filesem);
+ up_write(&common->luns->filesem);
+ down_read(&common->luns->filesem);

return common->ops && common->ops->post_eject
? min(0, common->ops->post_eject(common, curlun,
- curlun - common->luns))
+ curlun - common->luns->arr))
: 0;
}

@@ -1910,7 +1912,7 @@ static int check_command(struct fsg_common *common, int cmnd_size,

/* Check the LUN */
if (common->lun >= 0 && common->lun < common->nluns) {
- curlun = &common->luns[common->lun];
+ curlun = &common->luns->arr[common->lun];
common->curlun = curlun;
if (common->cmnd[0] != REQUEST_SENSE) {
curlun->sense_data = SS_NO_SENSE;
@@ -1986,7 +1988,8 @@ static int do_scsi_command(struct fsg_common *common)
common->phase_error = 0;
common->short_packet_received = 0;

- down_read(&common->filesem); /* We're using the backing file */
+ /* We're using the backing file */
+ down_read(&common->luns->filesem);
switch (common->cmnd[0]) {

case INQUIRY:
@@ -2219,7 +2222,7 @@ unknown_cmnd:
}
break;
}
- up_read(&common->filesem);
+ up_read(&common->luns->filesem);

if (reply == -EINTR || signal_pending(current))
return -EINTR;
@@ -2455,7 +2458,7 @@ reset:

common->running = 1;
for (i = 0; i < common->nluns; ++i)
- common->luns[i].unit_attention_data = SS_RESET_OCCURRED;
+ common->luns->arr[i].unit_attention_data = SS_RESET_OCCURRED;
return rc;
}

@@ -2555,7 +2558,7 @@ static void handle_exception(struct fsg_common *common)
common->state = FSG_STATE_STATUS_PHASE;
else {
for (i = 0; i < common->nluns; ++i) {
- curlun = &common->luns[i];
+ curlun = &common->luns->arr[i];
curlun->prevent_medium_removal = 0;
curlun->sense_data = SS_NO_SENSE;
curlun->unit_attention_data = SS_NO_SENSE;
@@ -2597,7 +2600,7 @@ static void handle_exception(struct fsg_common *common)
* CONFIG_CHANGE cases.
*/
/* for (i = 0; i < common->nluns; ++i) */
- /* common->luns[i].unit_attention_data = */
+ /* common->luns->arr[i].unit_attention_data = */
/* SS_RESET_OCCURRED; */
break;

@@ -2692,10 +2695,10 @@ static int fsg_main_thread(void *common_)

if (!common->ops || !common->ops->thread_exits
|| common->ops->thread_exits(common) < 0) {
- struct fsg_lun *curlun = common->luns;
+ struct fsg_lun *curlun = common->luns->arr;
unsigned i = common->nluns;

- down_write(&common->filesem);
+ down_write(&common->luns->filesem);
for (; i--; ++curlun) {
if (!fsg_lun_is_open(curlun))
continue;
@@ -2703,7 +2706,7 @@ static int fsg_main_thread(void *common_)
fsg_lun_close(curlun);
curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
}
- up_write(&common->filesem);
+ up_write(&common->luns->filesem);
}

/* Let fsg_unbind() know the thread has exited */
@@ -2723,9 +2726,30 @@ static DEVICE_ATTR(file, 0644, fsg_show_file, fsg_store_file);

static void fsg_common_release(struct kref *ref);

+static void fsg_luns_release(struct kref *ref)
+{
+ struct fsg_luns *luns = container_of(ref, struct fsg_luns, ref);
+ kfree(luns);
+}
+
static void fsg_lun_release(struct device *dev)
{
- /* Nothing needs to be done */
+ struct rw_semaphore *filesem = dev_get_drvdata(dev);
+ struct fsg_luns *luns =
+ container_of(filesem, struct fsg_luns, filesem);
+
+ /*
+ * This should be a no-op but something funky may have
+ * happened and the file may have been opened. Make sure and
+ * coles it.
+ */
+ fsg_lun_close(container_of(dev, struct fsg_lun, dev));
+
+ /*
+ * When all devices are released, the under-laying memory with
+ * accompanying filesem will be freed.
+ */
+ kref_put(&luns->ref, fsg_luns_release);
}

static inline void fsg_common_get(struct fsg_common *common)
@@ -2787,14 +2811,16 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common,
* Create the LUNs, open their backing files, and register the
* LUN devices in sysfs.
*/
- curlun = kzalloc(nluns * sizeof *curlun, GFP_KERNEL);
- if (unlikely(!curlun)) {
+ common->luns = kzalloc(sizeof *common->luns +
+ nluns * sizeof *common->luns->arr, GFP_KERNEL);
+ if (unlikely(!common->luns)) {
rc = -ENOMEM;
goto error_release;
}
- common->luns = curlun;
+ curlun = common->luns->arr;

- init_rwsem(&common->filesem);
+ init_rwsem(&common->luns->filesem);
+ kref_init(&common->luns->ref);

for (i = 0, lcfg = cfg->luns; i < nluns; ++i, ++curlun, ++lcfg) {
curlun->cdrom = !!lcfg->cdrom;
@@ -2803,13 +2829,14 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common,
curlun->dev.release = fsg_lun_release;
curlun->dev.parent = &gadget->dev;
/* curlun->dev.driver = &fsg_driver.driver; XXX */
- dev_set_drvdata(&curlun->dev, &common->filesem);
+ dev_set_drvdata(&curlun->dev, &common->luns->filesem);
dev_set_name(&curlun->dev,
cfg->lun_name_format
? cfg->lun_name_format
: "lun%d",
i);

+ kref_get(&common->luns->ref);
rc = device_register(&curlun->dev);
if (rc) {
INFO(common, "failed to register LUN%d: %d\n", i, rc);
@@ -2872,7 +2899,7 @@ buffhds_first_it:
snprintf(common->inquiry_string, sizeof common->inquiry_string,
"%-8s%-16s%04x", cfg->vendor_name ?: "Linux",
/* Assume product name dependent on the first LUN */
- cfg->product_name ?: (common->luns->cdrom
+ cfg->product_name ?: (common->luns->arr->cdrom
? "File-Stor Gadget"
: "File-CD Gadget"),
i);
@@ -2904,7 +2931,7 @@ buffhds_first_it:
INFO(common, "Number of LUNs=%d\n", common->nluns);

pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
- for (i = 0, nluns = common->nluns, curlun = common->luns;
+ for (i = 0, nluns = common->nluns, curlun = common->luns->arr;
i < nluns;
++curlun, ++i) {
char *p = "(no medium)";
@@ -2950,8 +2977,8 @@ static void fsg_common_release(struct kref *ref)
wait_for_completion(&common->thread_notifier);
}

- if (likely(common->luns)) {
- struct fsg_lun *lun = common->luns;
+ if (likely(common->luns->arr)) {
+ struct fsg_lun *lun = common->luns->arr;
unsigned i = common->nluns;

/* In error recovery common->nluns may be zero. */
@@ -2963,7 +2990,7 @@ static void fsg_common_release(struct kref *ref)
device_unregister(&lun->dev);
}

- kfree(common->luns);
+ kref_put(&common->luns->ref, fsg_luns_release);
}

{
--
1.7.2.3


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