target/file: Use O_DSYNC by default for FILEIO backends

commit a4dff3043c231d57f982af635c9d2192ee40e5ae upstream.

Convert to use O_DSYNC for all cases at FILEIO backend creation time to
avoid the extra syncing of pure timestamp updates with legacy O_SYNC during
default operation as recommended by hch.  Continue to do this independently of
Write Cache Enable (WCE) bit, as WCE=0 is currently the default for all backend
devices and enabled by user on per device basis via attrib/emulate_write_cache.

This patch drops the now unnecessary fd_buffered_io= token usage that was
originally signalling when to explictly disable O_SYNC at backend creation
time for buffered I/O operation.  This can end up being dangerous for a number
of reasons during physical node failure, so go ahead and drop this option
for now when O_DSYNC is used as the default.

Also allow explict FUA WRITEs -> vfs_fsync_range() call to function in
fd_execute_cmd() independently of WCE bit setting.

Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[bwh: Backported to 3.2:
 - We have fd_do_task() and not fd_execute_cmd()
 - Various fields are in struct se_task rather than struct se_cmd
 - fd_create_virtdevice() flags initialisation hasn't been cleaned up]

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index cad8b92..455a251 100644 (file)
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -134,21 +134,11 @@ static struct se_device *fd_create_virtdevice(
                ret = PTR_ERR(dev_p);
                goto fail;
        }
-#if 0
-       if (di->no_create_file)
-               flags = O_RDWR | O_LARGEFILE;
-       else
-               flags = O_RDWR | O_CREAT | O_LARGEFILE;
-#else
-       flags = O_RDWR | O_CREAT | O_LARGEFILE;
-#endif
-/*     flags |= O_DIRECT; */
        /*
-        * If fd_buffered_io=1 has not been set explicitly (the default),
-        * use O_SYNC to force FILEIO writes to disk.
+        * Use O_DSYNC by default instead of O_SYNC to forgo syncing
+        * of pure timestamp updates.
         */
-       if (!(fd_dev->fbd_flags & FDBD_USE_BUFFERED_IO))
-               flags |= O_SYNC;
+       flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;
 
        file = filp_open(dev_p, flags, 0600);
        if (IS_ERR(file)) {
@@ -400,26 +390,6 @@ static void fd_emulate_sync_cache(struct se_task *task)
                transport_complete_sync_cache(cmd, ret == 0);
 }
 
-/*
- * WRITE Force Unit Access (FUA) emulation on a per struct se_task
- * LBA range basis..
- */
-static void fd_emulate_write_fua(struct se_cmd *cmd, struct se_task *task)
-{
-       struct se_device *dev = cmd->se_dev;
-       struct fd_dev *fd_dev = dev->dev_ptr;
-       loff_t start = task->task_lba * dev->se_sub_dev->se_dev_attrib.block_size;
-       loff_t end = start + task->task_size;
-       int ret;
-
-       pr_debug("FILEIO: FUA WRITE LBA: %llu, bytes: %u\n",
-                       task->task_lba, task->task_size);
-
-       ret = vfs_fsync_range(fd_dev->fd_file, start, end, 1);
-       if (ret != 0)
-               pr_err("FILEIO: vfs_fsync_range() failed: %d\n", ret);
-}
-
 static int fd_do_task(struct se_task *task)
 {
        struct se_cmd *cmd = task->task_se_cmd;
@@ -434,19 +404,21 @@ static int fd_do_task(struct se_task *task)
                ret = fd_do_readv(task);
        } else {
                ret = fd_do_writev(task);
-
+               /*
+                * Perform implict vfs_fsync_range() for fd_do_writev() ops
+                * for SCSI WRITEs with Forced Unit Access (FUA) set.
+                * Allow this to happen independent of WCE=0 setting.
+                */
                if (ret > 0 &&
-                   dev->se_sub_dev->se_dev_attrib.emulate_write_cache > 0 &&
                    dev->se_sub_dev->se_dev_attrib.emulate_fua_write > 0 &&
                    (cmd->se_cmd_flags & SCF_FUA)) {
-                       /*
-                        * We might need to be a bit smarter here
-                        * and return some sense data to let the initiator
-                        * know the FUA WRITE cache sync failed..?
-                        */
-                       fd_emulate_write_fua(cmd, task);
-               }
+                       struct fd_dev *fd_dev = dev->dev_ptr;
+                       loff_t start = task->task_lba *
+                               dev->se_sub_dev->se_dev_attrib.block_size;
+                       loff_t end = start + task->task_size;
 
+                       vfs_fsync_range(fd_dev->fd_file, start, end, 1);
+               }
        }
 
        if (ret < 0) {
@@ -478,7 +450,6 @@ enum {
 static match_table_t tokens = {
        {Opt_fd_dev_name, "fd_dev_name=%s"},
        {Opt_fd_dev_size, "fd_dev_size=%s"},
-       {Opt_fd_buffered_io, "fd_buffered_io=%d"},
        {Opt_err, NULL}
 };
 
@@ -490,7 +461,7 @@ static ssize_t fd_set_configfs_dev_params(
        struct fd_dev *fd_dev = se_dev->se_dev_su_ptr;
        char *orig, *ptr, *arg_p, *opts;
        substring_t args[MAX_OPT_ARGS];
-       int ret = 0, arg, token;
+       int ret = 0, token;
 
        opts = kstrdup(page, GFP_KERNEL);
        if (!opts)
@@ -534,19 +505,6 @@ static ssize_t fd_set_configfs_dev_params(
                                        " bytes\n", fd_dev->fd_dev_size);
                        fd_dev->fbd_flags |= FBDF_HAS_SIZE;
                        break;
-               case Opt_fd_buffered_io:
-                       match_int(args, &arg);
-                       if (arg != 1) {
-                               pr_err("bogus fd_buffered_io=%d value\n", arg);
-                               ret = -EINVAL;
-                               goto out;
-                       }
-
-                       pr_debug("FILEIO: Using buffered I/O"
-                               " operations for struct fd_dev\n");
-
-                       fd_dev->fbd_flags |= FDBD_USE_BUFFERED_IO;
-                       break;
                default:
                        break;
                }
@@ -578,10 +536,8 @@ static ssize_t fd_show_configfs_dev_params(
        ssize_t bl = 0;
 
        bl = sprintf(b + bl, "TCM FILEIO ID: %u", fd_dev->fd_dev_id);
-       bl += sprintf(b + bl, "        File: %s  Size: %llu  Mode: %s\n",
-               fd_dev->fd_dev_name, fd_dev->fd_dev_size,
-               (fd_dev->fbd_flags & FDBD_USE_BUFFERED_IO) ?
-               "Buffered" : "Synchronous");
+       bl += sprintf(b + bl, "        File: %s  Size: %llu  Mode: O_DSYNC\n",
+               fd_dev->fd_dev_name, fd_dev->fd_dev_size);
        return bl;
 }
 

diff --git a/drivers/target/target_core_file.h b/drivers/target/target_core_file.h
index 59e6e73..53ece69 100644 (file)
--- a/drivers/target/target_core_file.h
+++ b/drivers/target/target_core_file.h
@@ -18,7 +18,6 @@ struct fd_request {
 
 #define FBDF_HAS_PATH          0x01
 #define FBDF_HAS_SIZE          0x02
-#define FDBD_USE_BUFFERED_IO   0x04
 
 struct fd_dev {
        u32             fbd_flags;