Messages in this thread Patch in this message | | | From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 179/180] ext4: allocate entire range in zero range | Date | Thu, 7 May 2015 10:46:28 +0100 |
| |
3.16.7-ckt11 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Lukas Czerner <lczerner@redhat.com>
commit 0f2af21aae11972fa924374ddcf52e88347cf5a8 upstream.
Currently there is a bug in zero range code which causes zero range calls to only allocate block aligned portion of the range, while ignoring the rest in some cases.
In some cases, namely if the end of the range is past i_size, we do attempt to preallocate the last nonaligned block. However this might cause kernel to BUG() in some carefully designed zero range requests on setups where page size > block size.
Fix this problem by first preallocating the entire range, including the nonaligned edges and converting the written extents to unwritten in the next step. This approach will also give us the advantage of having the range to be as linearly contiguous as possible.
Signed-off-by: Lukas Czerner <lczerner@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: Moritz Muehlenhoff <jmm@debian.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- fs/ext4/extents.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 2a4b4f3b1ae2..cdfe574ba3d9 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4795,12 +4795,6 @@ static long ext4_zero_range(struct file *file, loff_t offset, else max_blocks -= lblk; - flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT | - EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | - EXT4_EX_NOCACHE; - if (mode & FALLOC_FL_KEEP_SIZE) - flags |= EXT4_GET_BLOCKS_KEEP_SIZE; - mutex_lock(&inode->i_mutex); /* @@ -4817,15 +4811,28 @@ static long ext4_zero_range(struct file *file, loff_t offset, ret = inode_newsize_ok(inode, new_size); if (ret) goto out_mutex; - /* - * If we have a partial block after EOF we have to allocate - * the entire block. - */ - if (partial_end) - max_blocks += 1; } + flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT; + if (mode & FALLOC_FL_KEEP_SIZE) + flags |= EXT4_GET_BLOCKS_KEEP_SIZE; + + /* Preallocate the range including the unaligned edges */ + if (partial_begin || partial_end) { + ret = ext4_alloc_file_blocks(file, + round_down(offset, 1 << blkbits) >> blkbits, + (round_up((offset + len), 1 << blkbits) - + round_down(offset, 1 << blkbits)) >> blkbits, + new_size, flags, mode); + if (ret) + goto out_mutex; + + } + + /* Zero range excluding the unaligned edges */ if (max_blocks > 0) { + flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | + EXT4_EX_NOCACHE); /* Now release the pages and zero block aligned part of pages*/ truncate_pagecache_range(inode, start, end - 1);
| |