From: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx> (cherry picked from commit 2a8964d63d50dd2d65d71d342bc7fb6ef4117614) --- fs/ext4/inode.c | 13 +++++++++++++ 1 files changed, 13 insertions(+), 0 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 4ed5e92..b3d7250 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1076,6 +1076,7 @@ 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 @@ -1106,6 +1107,18 @@ 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() -- 1.6.3.1.1.g75fc.dirty -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
