target: Fix bug in handling of FILEIO + block_device resize ops

This patch fixes a bug in the handling of FILEIO w/ underlying block_device
resize operations where the original fd_dev->fd_dev_size was incorrectly being
used in fd_get_blocks() for READ_CAPACITY response payloads.

This patch avoids using fd_dev->fd_dev_size for FILEIO devices with
an underlying block_device, and instead changes fd_get_blocks() to
get the sector count directly from i_size_read() as recommended by hch.

Reported-by: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 16 insertions, 6 deletions

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index 7ed58e2df791..f286955331a2 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -169,6 +169,7 @@ static struct se_device *fd_create_virtdevice(
         inode = file->f_mapping->host;
         if (S_ISBLK(inode->i_mode)) {
                 struct request_queue *q;
+                unsigned long long dev_size;
                 /*
                  * Setup the local scope queue_limits from struct request_queue->limits
                  * to pass into transport_add_device_to_core_hba() as struct se_dev_limits.
@@ -183,13 +184,12 @@ static struct se_device *fd_create_virtdevice(
                  * one (1) logical sector from underlying struct block_device
                  */
                 fd_dev->fd_block_size = bdev_logical_block_size(inode->i_bdev);
-                fd_dev->fd_dev_size = (i_size_read(file->f_mapping->host) -
+                dev_size = (i_size_read(file->f_mapping->host) -
                                        fd_dev->fd_block_size);
 
                 pr_debug("FILEIO: Using size: %llu bytes from struct"
                         " block_device blocks: %llu logical_block_size: %d\n",
-                        fd_dev->fd_dev_size,
-                        div_u64(fd_dev->fd_dev_size, fd_dev->fd_block_size),
+                        dev_size, div_u64(dev_size, fd_dev->fd_block_size),
                         fd_dev->fd_block_size);
         } else {
                 if (!(fd_dev->fbd_flags & FBDF_HAS_SIZE)) {
@@ -605,10 +605,20 @@ static u32 fd_get_device_type(struct se_device *dev)
 static sector_t fd_get_blocks(struct se_device *dev)
 {
         struct fd_dev *fd_dev = dev->dev_ptr;
-        unsigned long long blocks_long = div_u64(fd_dev->fd_dev_size,
-                        dev->se_sub_dev->se_dev_attrib.block_size);
+        struct file *f = fd_dev->fd_file;
+        struct inode *i = f->f_mapping->host;
+        unsigned long long dev_size;
+        /*
+         * When using a file that references an underlying struct block_device,
+         * ensure dev_size is always based on the current inode size in order
+         * to handle underlying block_device resize operations.
+         */
+        if (S_ISBLK(i->i_mode))
+                dev_size = (i_size_read(i) - fd_dev->fd_block_size);
+        else
+                dev_size = fd_dev->fd_dev_size;
 
-        return blocks_long;
+        return div_u64(dev_size, dev->se_sub_dev->se_dev_attrib.block_size);
 }
 
 static struct se_subsystem_api fileio_template = {