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[dm-devel] [PATCH] use i_size_read() instead of i_size



Use i_size_read() instead of reading i_size.

If someone changes the size of the device simultaneously, i_size_read
is guaranteed to return a valid value (either the old one or the new one).

i_size can return some intermediate invalid value (on 32-bit computers
with 64-bit i_size, the reads to both halves of i_size can be interleaved
with updates to i_size, resulting in garbage being returned).

Signed-off-by: Mikulas Patocka <mpatocka redhat com>

---
 drivers/md/dm-exception-store.h |    2 +-
 drivers/md/dm-log.c             |    2 +-
 drivers/md/dm-table.c           |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

Index: linux-2.6.30-rc5-fast/drivers/md/dm-exception-store.h
===================================================================
--- linux-2.6.30-rc5-fast.orig/drivers/md/dm-exception-store.h	2009-05-18 17:29:01.000000000 +0200
+++ linux-2.6.30-rc5-fast/drivers/md/dm-exception-store.h	2009-05-18 17:29:24.000000000 +0200
@@ -156,7 +156,7 @@ static inline void dm_consecutive_chunk_
  */
 static inline sector_t get_dev_size(struct block_device *bdev)
 {
-	return bdev->bd_inode->i_size >> SECTOR_SHIFT;
+	return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
 }
 
 static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
Index: linux-2.6.30-rc5-fast/drivers/md/dm-log.c
===================================================================
--- linux-2.6.30-rc5-fast.orig/drivers/md/dm-log.c	2009-05-18 17:29:32.000000000 +0200
+++ linux-2.6.30-rc5-fast/drivers/md/dm-log.c	2009-05-18 17:29:42.000000000 +0200
@@ -431,7 +431,7 @@ static int create_log_context(struct dm_
 		buf_size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) +
 				       bitset_size, ti->limits.hardsect_size);
 
-		if (buf_size > dev->bdev->bd_inode->i_size) {
+		if (buf_size > i_size_read(dev->bdev->bd_inode)) {
 			DMWARN("log device %s too small: need %llu bytes",
 				dev->name, (unsigned long long)buf_size);
 			kfree(lc);
Index: linux-2.6.30-rc5-fast/drivers/md/dm-table.c
===================================================================
--- linux-2.6.30-rc5-fast.orig/drivers/md/dm-table.c	2009-05-18 17:29:46.000000000 +0200
+++ linux-2.6.30-rc5-fast/drivers/md/dm-table.c	2009-05-18 17:29:57.000000000 +0200
@@ -387,7 +387,7 @@ static void close_dev(struct dm_dev_inte
 static int device_area_is_valid(struct dm_target *ti, struct block_device *bdev,
 			     sector_t start, sector_t len)
 {
-	sector_t dev_size = bdev->bd_inode->i_size >> SECTOR_SHIFT;
+	sector_t dev_size = i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
 	unsigned short hardsect_size_sectors = ti->limits.hardsect_size >>
 					       SECTOR_SHIFT;
 	char b[BDEVNAME_SIZE];


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