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| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2009-05-12 16:30:27 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2009-05-12 16:30:27 -0400 |
| commit | 29fa89d088941d79765d60f22d5ccdd6b8696e11 (patch) | |
| tree | 3fbe031eec140c03dafa11f2416c4f6e3826f21d /fs/ext4/extents.c | |
| parent | 8fb0e342481c4d80040670fec915f0b9c7c6499a (diff) | |
| download | talos-op-linux-29fa89d088941d79765d60f22d5ccdd6b8696e11.tar.gz talos-op-linux-29fa89d088941d79765d60f22d5ccdd6b8696e11.zip | |
ext4: Mark the unwritten buffer_head as mapped during write_begin
Setting BH_Unwritten buffer_heads as BH_Mapped avoids multiple
(unnecessary) calls to get_block() during the call to the write(2)
system call. Setting BH_Unwritten buffer heads as BH_Mapped requires
that the writepages() functions can handle BH_Unwritten buffer_heads.
After this commit, things work as follows:
ext4_ext_get_block() returns unmapped, unwritten, buffer head when
called with create = 0 for prealloc space. This makes sure we handle
the read path and non-delayed allocation case correctly. Even though
the buffer head is marked unmapped we have valid b_blocknr and b_bdev
values in the buffer_head.
ext4_da_get_block_prep() called for block resrevation will now return
mapped, unwritten, new buffer_head for prealloc space. This avoids
multiple calls to get_block() for write to same offset. By making such
buffers as BH_New, we also assure that sub-block zeroing of buffered
writes happens correctly.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/extents.c')
| -rw-r--r-- | fs/ext4/extents.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index a953214f2829..ea5c47608cea 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -2872,6 +2872,8 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, if (create == EXT4_CREATE_UNINITIALIZED_EXT) goto out; if (!create) { + if (allocated > max_blocks) + allocated = max_blocks; /* * We have blocks reserved already. We * return allocated blocks so that delalloc @@ -2879,8 +2881,6 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, * the buffer head will be unmapped so that * a read from the block returns 0s. */ - if (allocated > max_blocks) - allocated = max_blocks; set_buffer_unwritten(bh_result); bh_result->b_bdev = inode->i_sb->s_bdev; bh_result->b_blocknr = newblock; |
