target: Fix PR_APTPL_BUF_LEN buffer size limitation

This patch addresses the original PR_APTPL_BUF_LEN = 8k limitiation
for write-out of PR APTPL metadata that Martin has recently been
running into.

It changes core_scsi3_update_and_write_aptpl() to use vzalloc'ed
memory instead of kzalloc, and increases the default hardcoded
length to 256k.

It also adds logic in core_scsi3_update_and_write_aptpl() to double
the original length upon core_scsi3_update_aptpl_buf() failure, and
retries until the vzalloc'ed buffer is large enough to accommodate
the outgoing APTPL metadata.

Reported-by: Martin Svec <martin.svec@zoner.cz>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 13 insertions, 12 deletions

diff --git a/drivers/target/target_core_pr.c b/drivers/target/target_core_pr.c
index d56f2aaba9af..67fb3bf240cd 100644
--- a/drivers/target/target_core_pr.c
+++ b/drivers/target/target_core_pr.c
@@ -1862,8 +1862,8 @@ static int core_scsi3_update_aptpl_buf(
                 }
 
                 if ((len + strlen(tmp) >= pr_aptpl_buf_len)) {
-                        pr_err("Unable to update renaming"
-                                " APTPL metadata\n");
+                        pr_err("Unable to update renaming APTPL metadata,"
+                               " reallocating larger buffer\n");
                         ret = -EMSGSIZE;
                         goto out;
                 }
@@ -1880,8 +1880,8 @@ static int core_scsi3_update_aptpl_buf(
                         lun->lun_sep->sep_rtpi, lun->unpacked_lun, reg_count);
 
                 if ((len + strlen(tmp) >= pr_aptpl_buf_len)) {
-                        pr_err("Unable to update renaming"
-                                " APTPL metadata\n");
+                        pr_err("Unable to update renaming APTPL metadata,"
+                               " reallocating larger buffer\n");
                         ret = -EMSGSIZE;
                         goto out;
                 }
@@ -1944,7 +1944,7 @@ static int __core_scsi3_write_aptpl_to_file(
 static sense_reason_t core_scsi3_update_and_write_aptpl(struct se_device *dev, bool aptpl)
 {
         unsigned char *buf;
-        int rc;
+        int rc, len = PR_APTPL_BUF_LEN;
 
         if (!aptpl) {
                 char *null_buf = "No Registrations or Reservations\n";
@@ -1958,25 +1958,26 @@ static sense_reason_t core_scsi3_update_and_write_aptpl(struct se_device *dev, b
 
                 return 0;
         }
-
-        buf = kzalloc(PR_APTPL_BUF_LEN, GFP_KERNEL);
+retry:
+        buf = vzalloc(len);
         if (!buf)
                 return TCM_OUT_OF_RESOURCES;
 
-        rc = core_scsi3_update_aptpl_buf(dev, buf, PR_APTPL_BUF_LEN);
+        rc = core_scsi3_update_aptpl_buf(dev, buf, len);
         if (rc < 0) {
-                kfree(buf);
-                return TCM_OUT_OF_RESOURCES;
+                vfree(buf);
+                len *= 2;
+                goto retry;
         }
 
         rc = __core_scsi3_write_aptpl_to_file(dev, buf);
         if (rc != 0) {
                 pr_err("SPC-3 PR: Could not update APTPL\n");
-                kfree(buf);
+                vfree(buf);
                 return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
         }
         dev->t10_pr.pr_aptpl_active = 1;
-        kfree(buf);
+        vfree(buf);
         pr_debug("SPC-3 PR: Set APTPL Bit Activated\n");
         return 0;
 }