xfs: Fix overallocation in xfs_buf_allocate_memory()
Commit de1cbee4 which removed b_file_offset in favor of b_bn introduced a bug causing xfs_buf_allocate_memory() to overestimate the number of necessary pages. The problem is that xfs_buf_alloc() sets b_bn to -1 and thus effectively every buffer is straddling a page boundary which causes xfs_buf_allocate_memory() to allocate two pages and use vmalloc() for access which is unnecessary. Dave says xfs_buf_alloc() doesn't need to set b_bn to -1 anymore since the buffer is inserted into the cache only after being fully initialized now. So just make xfs_buf_alloc() fill in proper block number from the beginning. CC: David Chinner <dchinner@redhat.com> Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Ben Myers <bpm@sgi.com>
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