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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2009-06-02 08:09:35 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2009-06-11 20:01:59 -0700
commitef3740934e85572dce2e20cecea3341fd43647e0 (patch)
treeeb5fd1e19b3036f605917956b6520960bc2e4b38
parentf0e70fb39944b1345203ab72d4c6117da6bf072a (diff)
ext4: Clear the unwritten buffer_head flag after the extent is initialized
(cherry picked from commit 2a8964d63d50dd2d65d71d342bc7fb6ef4117614) 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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-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 40519bddce0c..aeebfc255169 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1085,6 +1085,7 @@ 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
@@ -1115,6 +1116,18 @@ 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()