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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2009-05-14 17:05:39 -0400
committerTheodore Ts'o <tytso@mit.edu>2009-05-14 17:05:39 -0400
commit2a8964d63d50dd2d65d71d342bc7fb6ef4117614 (patch)
tree7dd80d63afd9adab61ba0695ac3e0c95485dc2ed
parent33b9817e2ae097c7b8d256e3510ac6c54fc6d9d0 (diff)
ext4: Clear the unwritten buffer_head flag after the extent is initialized
The BH_Unwritten flag indicates that the buffer is allocated on disk but has not been written; that is, the disk was part of a persistent preallocation area. That flag should only be set when a get_blocks() function is looking up a inode's logical to physical block mapping. When ext4_get_blocks_wrap() is called with create=1, the uninitialized extent is converted into an initialized one, so the BH_Unwritten flag is no longer appropriate. Hence, we need to make sure the BH_Unwritten is not left set, since the combination of BH_Mapped and BH_Unwritten is not allowed; among other things, it will result ext4's get_block() to be called over and over again during the write_begin phase of write(2). Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
-rw-r--r--fs/ext4/inode.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0ac31a06422b..2a9ffd528dd1 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1149,6 +1149,7 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
int retval;
clear_buffer_mapped(bh);
+ clear_buffer_unwritten(bh);
/*
* Try to see if we can get the block without requesting
@@ -1179,6 +1180,18 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
return retval;
/*
+ * When we call get_blocks without the create flag, the
+ * BH_Unwritten flag could have gotten set if the blocks
+ * requested were part of a uninitialized extent. We need to
+ * clear this flag now that we are committed to convert all or
+ * part of the uninitialized extent to be an initialized
+ * extent. This is because we need to avoid the combination
+ * of BH_Unwritten and BH_Mapped flags being simultaneously
+ * set on the buffer_head.
+ */
+ clear_buffer_unwritten(bh);
+
+ /*
* New blocks allocate and/or writing to uninitialized extent
* will possibly result in updating i_data, so we take
* the write lock of i_data_sem, and call get_blocks()